Android development learning (2)

Enterprise 2022-10-17 01:03:21 views: null

Article directory

1. Notification of the control (notification bar)

1.1 Use of NotificationManager and attention to details

The NotificationManager class is a notification manager class. This object is obtained by a service maintained by the system in a singleton mode, so this object is generally not instantiated directly.

In an Activity, you can use the Activity.getSystemService(String) method to get the NotificationManager object.

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The Notification object is created through the Builder constructor of the NotificationCompat class.

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Android8.0 added the concept of channel, if it is not set, the notification cannot be displayed on the Android8.0 machine!

The role of Build.VERSION.SDK_INT:

  • Build.VERSION.SDK_INT On which mobile phone the software app is installed, the version number of the operating system of the mobile phone, for example, the corresponding SDK_INT of 8.1 is 27

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The importance of the third parameter of the NotificationChannel object:
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1.2 Use of notification

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To achieve the effect of notification:
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Code case:

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical"
    >

    <Button
        android:text="发出通知"
        android:onClick="sendNotification"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"/>

    <Button
        android:text="取消通知"
        android:onClick="cancelNotification"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"/>

</LinearLayout>

Intent trigger class:

package com.example.mynotification;

import android.app.Activity;
import android.os.Bundle;
import android.util.Log;

import androidx.annotation.Nullable;

public class NotificationActivity extends Activity {
    
    

    @Override
    protected void onCreate(@Nullable Bundle savedInstanceState) {
    
    
        super.onCreate(savedInstanceState);
        Log.e("itholmes","onCreate: 进入NotificationActivity");
    }

}

The notification class defines the configuration, triggering and other effects:

package com.example.mynotification;

import androidx.appcompat.app.AppCompatActivity;
import androidx.core.app.NotificationCompat;

import android.app.Notification;
import android.app.NotificationChannel;
import android.app.NotificationManager;
import android.app.PendingIntent;
import android.content.Intent;
import android.graphics.BitmapFactory;
import android.graphics.Color;
import android.os.Build;
import android.os.Bundle;
import android.view.View;

public class MainActivity extends AppCompatActivity {
    
    

    private NotificationManager manager;

    private Notification notification;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
    
    
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        // 通过getSystemService获取NotificationManager对象。
        manager = (NotificationManager) getSystemService(NOTIFICATION_SERVICE);

        /**
         * 如果是android 8版本必须配置渠道：
         *   Build.VERSION.SDK_INT: 是获取软件app安装在哪个手机上，该手机的操作系统的版本号 比如8.1对应的SDK_INT是27
         *   NotificationManager.IMPORTANCE_HIGH: 该值为26是android API版本，对应Android 8.0(Oreo)版本。
         */
        if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.O){
    
    
            NotificationChannel channel = new NotificationChannel("itholmes", "测试通知", NotificationManager.IMPORTANCE_HIGH);
            manager.createNotificationChannel(channel);
        }

        // 创建意图， 方便下面跳转意图。
        Intent intent = new Intent(this, NotificationActivity.class);
        PendingIntent pendingIntent = PendingIntent.getActivity(this, 0, intent, 0);

        // 通过NotificationCompat类的Builder构造器创建Notification
        notification = new NotificationCompat.Builder(this,"itholmes")
                // 设置标题
                .setContentTitle("官方通知")
                // 设置内容
                .setContentText("世界那么大，想去走走")
                // 设置小图标，R.drawable.logo就是drawable目录下面的logo图片。
                .setSmallIcon(R.drawable.logo)
                // 设置大图标，BitmapFactory.decodeResource将图片转换Bitmap形式。
                .setLargeIcon(BitmapFactory.decodeResource(getResources(),R.drawable.logo))
                // 设置小图标的颜色 Color.parseColor方法将颜色转换为int类型。
                .setColor(Color.parseColor("#ff0000"))
                // 设置点击通知后的跳转意图
                .setContentIntent(pendingIntent)
                // 设置点击通知后自动清除通知
                .setAutoCancel(true)
                // .setWhen() 默认设置为当前时间
                .build();

    }

    public void sendNotification(View view){
    
    
        // 调用notify方法来触发通知。 注意：id就是唯一标识的效果。
        manager.notify(1,notification);
    }

    public void cancelNotification(View view){
    
    
        // 调用cancel方法来取消通知。
        manager.cancel(1);
    }

}

2. Toolbar of the control (toolbar, personally feel like a navigation bar)

For the newly created project, you can remove the original actionBar first:
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This time, the Toolbar of androidx is used.

Basic properties of Toolbar:
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An example is as follows:

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    android:orientation="vertical">

    <!-- 方式一：基本属性的使用 -->
    <androidx.appcompat.widget.Toolbar
        android:id="@+id/td"

        app:navigationIcon="@drawable/ic_baseline_arrow_back_ios_new_24"

        app:title="标题"
        app:titleTextColor="#ff0000"
        app:titleMarginStart="90dp"

        app:subtitle="子标题"
        app:subtitleTextColor="#00ffff"

        app:logo="@mipmap/ic_launcher"

        android:layout_width="match_parent"
        android:layout_height="?attr/actionBarSize"
        android:background="#ffff00" />

    <!-- 方式二：实现标题居中的效果如下 -->
    <androidx.appcompat.widget.Toolbar
        android:id="@+id/td2"
        app:navigationIcon="@drawable/ic_baseline_arrow_back_ios_new_24"
        android:layout_width="match_parent"
        android:layout_height="?attr/actionBarSize"
        android:background="#ffff00" >

        <TextView
            android:text="标题"
            android:layout_gravity="center"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            />

        <!-- TextView 通过设置layout_gravity为center来达到居中的效果。 -->

    </androidx.appcompat.widget.Toolbar>

</LinearLayout>

package com.example.mytoolbar;

import androidx.appcompat.app.AppCompatActivity;
import androidx.appcompat.widget.Toolbar;

import android.os.Bundle;
import android.util.Log;
import android.view.View;


public class MainActivity extends AppCompatActivity {
    
    

    @Override
    protected void onCreate(Bundle savedInstanceState) {
    
    
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        Toolbar toolbar = findViewById(R.id.td);
        // 获取到toolbar，添加Navigation的点击事件(目前对应，navigationIcon属性设置的图片最左侧那个。)
        // 这样之后最左侧的被点击后，就回触发！
        toolbar.setNavigationOnClickListener(new View.OnClickListener() {
    
    
            @Override
            public void onClick(View view) {
    
    
                Log.e("TAG","toolbar被点击了");
            }
        });

    }
}

3. AlertDialog (dialog box) of the control

The effect is as follows:
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Basic properties:
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An example is as follows:

activity_main.xml

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    android:orientation="vertical">

    <Button
        android:text="显示对话框"
        android:onClick="dialClick"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"/>

</LinearLayout>

dialog_view.xml

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout
    android:layout_height="match_parent"
    android:layout_width="wrap_content"
    android:orientation="vertical"
    android:background="#ffff00"
    xmlns:android="http://schemas.android.com/apk/res/android">

    <ImageView
        android:src="@mipmap/ic_launcher"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"/>

    <TextView
        android:text="哈哈，天气很好"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"/>

</LinearLayout>

MainActivity

package com.example.mytoolbar;

import androidx.appcompat.app.AppCompatActivity;

import android.app.AlertDialog;
import android.content.DialogInterface;
import android.os.Bundle;
import android.util.Log;
import android.view.View;

public class MainActivity extends AppCompatActivity {
    
    

    @Override
    protected void onCreate(Bundle savedInstanceState) {
    
    
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
    }

    public void dialClick(View view){
    
    

        // 通过getLayoutInflater().inflate方法来获取layout布局信息
        View dialogView = getLayoutInflater().inflate(R.layout.dialog_view,null);

        AlertDialog.Builder builder = new AlertDialog.Builder(this);
        // 这些set方法返回的都是builder，因此可以连贯起来。
        builder
            // 设置图标
            .setIcon(R.mipmap.ic_launcher)
            // 设置标题
            .setTitle("我是对话框")
            // 设置消息
            .setMessage("今天天气怎么样！")
            // 设置一个布局视图
            .setView(dialogView)
            // 设置确认按钮
            .setPositiveButton("确定", new DialogInterface.OnClickListener() {
    
    
                @Override
                public void onClick(DialogInterface dialogInterface, int i) {
    
    
                    Log.e("tag","确认按钮被点击了");
                }
            })
            // 设置取消按钮
            .setNegativeButton("取消",new DialogInterface.OnClickListener() {
    
    
                @Override
                public void onClick(DialogInterface dialogInterface, int i) {
    
    
                    Log.e("tag","取消按钮被点击了");
                }
            })
            // 设置中间按钮
            .setNeutralButton("中间",new DialogInterface.OnClickListener() {
    
    
                @Override
                public void onClick(DialogInterface dialogInterface, int i) {
    
    
                    Log.e("tag","中间按钮被点击了");
                }
            });
        // 调用create方法创建一个AlertDialog对象
        AlertDialog alertDialog = builder.create();
        // 调用AlertDialog对象的show方法显示对话框
        alertDialog.show();
    }

}

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4. PopupWindow of the control (pop-up layer)

The basic properties are as follows:
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An example is as follows:

activity_main.xml

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout
    android:orientation="vertical"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    xmlns:android="http://schemas.android.com/apk/res/android">

    <Button
        android:text="弹出PopupWindow"
        android:onClick="popupClick"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"/>

</LinearLayout>

popup_view.xml

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:background="@mipmap/ic_launcher"
    android:orientation="vertical"
    android:layout_width="match_parent"
    android:layout_height="match_parent">

    <Button
        android:id="@+id/btn1"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:padding="5dp"
        android:text="上海" />

    <Button
        android:id="@+id/btn2"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:padding="5dp"
        android:text="关闭弹出层" />


</LinearLayout>

MainActivity

package com.example.mypopupwindow;

import androidx.appcompat.app.AppCompatActivity;

import android.os.Bundle;
import android.util.Log;
import android.view.View;
import android.view.ViewGroup;
import android.widget.Button;
import android.widget.PopupWindow;

public class MainActivity extends AppCompatActivity {
    
    

    @Override
    protected void onCreate(Bundle savedInstanceState) {
    
    
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
    }

    public void popupClick(View view){
    
    

        // 获取要设置在popupWindow里的布局
        View popupView = getLayoutInflater().inflate(R.layout.popup_view,null);

        /**
         * PopupWindow对象有参数构造器！
         *  第一个参数：设置在PopupWindow的布局。
         *  第二、三参数：一个宽，一个高，而ViewGroup.LayoutParams.WRAP_CONTENT是为了彻底包裹popupView布局视图。
         *  第四个参数：是否获取焦点。 该内容可以实现失去焦点，关闭弹出层效果。
         */
        PopupWindow popupWindow = new PopupWindow(
                popupView, ViewGroup.LayoutParams.WRAP_CONTENT,ViewGroup.LayoutParams.WRAP_CONTENT,true);


        // popupView中还有两个按钮
        Button btn1 = popupView.findViewById(R.id.btn1);
        btn1.setOnClickListener(new View.OnClickListener() {
    
    
            @Override
            public void onClick(View view) {
    
    
                Log.e("TAG","onclick上海按钮触发");
            }
        });
        Button btn2 = popupView.findViewById(R.id.btn2);
        btn2.setOnClickListener(new View.OnClickListener() {
    
    
            @Override
            public void onClick(View view) {
    
    
                // 关闭弹出层
                popupWindow.dismiss();
            }
        });


        // 设置背景
        popupWindow.setBackgroundDrawable(getResources().getDrawable(R.drawable.logo));

        // 相对某个控件的位置(正左下方)， 这里就直接让其显示在当前view的下方实际就是按钮。
        // 第二、三参数就是设置偏移量的，不填写就是无偏移
        // 可以通过view.getWidth()和view.getHeight()来贴合！ 也可以使用 - 负号
        // popupWindow.showAsDropDown(view,view.getWidth(),-view.getHeight());
        popupWindow.showAsDropDown(view);

    }

}

The effect is as follows:
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5. LinearLayout of the layout (layout)

Basic properties:
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The | in the middle of android:gravity="center_horizontal|bottom" is an OR statement. This property represents the effect of centering the bottom of the current layout.

android:divider=“@drawable/ic_launcher_background”
android:showDividers=“middle”, set the dividing line, in fact, the dividing line is to set the picture, showDivider is the display position (there is one between every two elements inside the middle layout)

android:layout_weight=“2”
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<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:gravity="center_horizontal"

    android:divider="@drawable/ic_baseline_drag_handle_24"
    android:showDividers="middle"
    android:dividerPadding="100dp"

    android:orientation="vertical">

    <LinearLayout
        android:layout_weight="2"
        android:layout_gravity="center_vertical"
        android:background="#ff0000"
        android:layout_width="100dp"
        android:layout_height="100dp">
    </LinearLayout>

    <LinearLayout
        android:layout_weight="1"
        android:background="#ffff00"
        android:layout_width="100dp"
        android:layout_height="100dp">

    </LinearLayout>

    <LinearLayout
        android:background="#00ffff"
        android:layout_width="100dp"
        android:layout_height="100dp">
    </LinearLayout>

</LinearLayout>

The effect is as follows:
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6. RelativeLayout of the layout (relative layout)

Basic properties:
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Attributes are also easy to distinguish. With parent, it is positioned according to the parent container.

  • The assigned value is either true or boolean.
<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    >
	<!-- 父子之间的相对定位。 -->
    <RelativeLayout
        android:layout_centerInParent="true"
        android:background="#ff0000"
        android:layout_width="100dp"
        android:layout_height="100dp"/>

</RelativeLayout>

Without the parent attribute, you need to specify the component id:
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7. Layout of FrameLayout (frame layout)

The effect is as follows:

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Basic properties:
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android:foreground="@drawable/ic_launcher_background"
android:foregroundGravity="right|center" , set a background image, and set the position.

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8. Layout of TableLayout (table layout)

Basic properties of TableLayout:
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The android:collapseColumns property uses:
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It can also be operated in the form of android:collapseColumns="0,2":
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android:stretchColumns="1" attribute: Specifies the columns that can be stretched (stretched for the remaining space).
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android:shrinkColumns="1" attribute: Set the columns that can be shrunk.

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layout_column attribute:
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android:layout_span="2" attribute: spans several columns.
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<?xml version="1.0" encoding="utf-8"?>
<TableLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:stretchColumns="1"
    android:shrinkColumns="1"
    >

    <!-- TableRow代表一行 -->
    <TableRow>
        <Button
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_column="2"
            android:layout_span="2"
            android:text="第1个"
            />

        <Button
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:text="第2个"
            />
    </TableRow>

    <TableRow>
        <Button
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:text="第1个"
            />

        <Button
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:text="第2个"
            />

        <Button
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:text="第3个"
            />

        <Button
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:text="第4个"
            />

        <Button
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:text="第5个"
            />

    </TableRow>

</TableLayout>

9. GridLayout (Grid Layout)

Basic properties of GridLayout:
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In fact, columnCount and rowCount control several columns and rows.
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Properties of child controls under GridLayout:
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An example is as follows:

<?xml version="1.0" encoding="utf-8"?>
<GridLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent"

    android:columnCount="4"
    android:rowCount="2"
    >
    <!-- 上面就是显示4列，2行的效果。其实columnCount和rowCount就是控制几列几行。 -->

    <Button
        android:text="第1个"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"/>

    <Button
        android:text="第2个"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"/>

    <Button
        android:text="第3个"

        android:layout_columnWeight="1"
        android:layout_rowWeight="1"

        android:layout_width="wrap_content"
        android:layout_height="wrap_content"/>

    <Button
        android:text="第4个"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"/>

    <Button
        android:text="第5个"
        android:layout_row="1"
        android:layout_column="0"

        android:layout_columnSpan="3"
        android:layout_gravity="fill"

        android:layout_width="wrap_content"
        android:layout_height="wrap_content"/>

</GridLayout>

10. ConstraintLayout of layout (constraint layout)

As shown below, to set the constraint layout:
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Related operations for controls:

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use of guidelines guidelines:
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Configuration view:
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Use of inference constraints:
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