ListView基础入门(获取手机应用并快速打开功能Demo)

其他 2018-05-14 19:11:30 阅读次数: 2

一、ListView基础案例

首先定义一个接收每一天item的布局

item.app.list.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"
    android:orientation="horizontal">

    <ImageView
        android:id="@+id/app_icon_image_view"
        android:layout_width="60dp"
        android:layout_height="60dp"
        android:src="@mipmap/ic_launcher"/>
    <TextView
        android:id="@+id/app_name_text_view"
        android:layout_width="60dp"
        android:layout_height="60dp"
        android:paddingLeft="6dp"
        android:textSize="20sp"
        android:gravity="center_vertical"
        android:text="@string/app_name"/>
</LinearLayout>

在activity_main.xml中定义一个ListView控件的摆放位置

activity_main.xml

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

    <ListView
        android:id="@+id/app_list_view"
        android:layout_width="match_parent"
        android:layout_height="match_parent">

    </ListView>

</LinearLayout>

创建一个Adapter适配器，将item不断的往ListView容器中填充

MainActivity.java

package com.administrator.listviewdemo;

import android.content.Context;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.BaseAdapter;
import android.widget.ImageView;
import android.widget.ListView;
import android.widget.TextView;

import java.util.ArrayList;
import java.util.List;

public class MainActivity extends AppCompatActivity {

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

        ListView app_list_view = (ListView)findViewById(R.id.app_list_view);
        List<String> appName = new ArrayList<>();
        appName.add("QQ");
        appName.add("微信");
        appName.add("haha");

        app_list_view.setAdapter(new AppListAdapter(appName));
    }

    /**
     * 定义适配器操作数据
     */
    public class AppListAdapter extends BaseAdapter{
        List<String> mAppNames;
        public AppListAdapter(List<String> appName){
            mAppNames = appName;
        }

        @Override
        public int getCount() {
            //有多少条数据
            return mAppNames.size();
        }

        @Override
        public Object getItem(int position) {
            //获取当前position位置的这一条
            return mAppNames.get(position);
        }

        @Override
        public long getItemId(int position) {
            //获取当前position位置的这一条的ID
            return position;
        }

        /**
         * 这里还应该写一个ViewHolder，考虑到初学者的理解方便，暂时不写
         */
        @Override
        public View getView(int position, View convertView, ViewGroup parent) {
            //处理 view--data 填充数据的一个过程
            LayoutInflater layoutInflater = (LayoutInflater) getSystemService(Context.LAYOUT_INFLATER_SERVICE);
            convertView = layoutInflater.inflate(R.layout.item_app_list,null);
            if(convertView != null){
                ImageView appIconImageViw = (ImageView)convertView.findViewById(R.id.app_icon_image_view);
                TextView appNameTextView = (TextView) convertView.findViewById(R.id.app_name_text_view);

                appNameTextView.setText(mAppNames.get(position));
            }
            return convertView;
        }
    }
}

ViewHolder有什么好处呢，因为TextView appNameTextView写在了ViewHolder里面，这样，getView方法就不用每次都去布局文件中拿View，提高了效率

二、使用listView制作获取手机应用并快速打开功能

item_app_list.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"
    android:orientation="horizontal">

    <ImageView
        android:id="@+id/app_icon_image_view"
        android:layout_width="60dp"
        android:layout_height="60dp"
        android:src="@mipmap/ic_launcher"/>
    <TextView
        android:id="@+id/app_name_text_view"
        android:layout_width="60dp"
        android:layout_height="60dp"
        android:paddingLeft="6dp"
        android:textSize="20sp"
        android:gravity="center_vertical"
        android:text="@string/app_name"/>
</LinearLayout>

header_list.xml

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

    <ImageView
        android:layout_width="match_parent"
        android:layout_height="60dp"
        android:src="@mipmap/ic_launcher"/>
</LinearLayout>

activity_main.xml

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

<ListView
    android:id="@+id/app_list_view"
    android:layout_width="match_parent"
    android:layout_height="match_parent">

</ListView>

</LinearLayout>
package com.administrator.listviewdemo;

import android.content.ComponentName;
import android.content.Context;
import android.content.Intent;
import android.content.pm.ComponentInfo;
import android.content.pm.ResolveInfo;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.AdapterView;
import android.widget.BaseAdapter;
import android.widget.ImageView;
import android.widget.ListView;
import android.widget.TextView;
import android.widget.Toast;

import java.util.ArrayList;
import java.util.List;

public class MainActivity extends AppCompatActivity {

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

        ListView app_list_view = (ListView)findViewById(R.id.app_list_view);


        //添加标题的headerView
        //解析LayoutInflater
        LayoutInflater layoutInflater = (LayoutInflater)getSystemService(Context.LAYOUT_INFLATER_SERVICE);
        View headerView = layoutInflater.inflate(R.layout.header_list,null);
        app_list_view.addHeaderView(headerView);


        final List<ResolveInfo> appInfos = getAppInfos();
        app_list_view.setAdapter(new AppListAdapter(getAppInfos()));


        /**
         * ListView在外面调用的方法
         */
        app_list_view.setOnItemClickListener(new AdapterView.OnItemClickListener() {
            @Override
            public void onItemClick(AdapterView<?> parent, View view, int position, long id) {
                    //拿到应用的包名
                    String packageName = appInfos.get(position).activityInfo.packageName;
                    //拿到主要的类名
                    String classString = appInfos.get(position).activityInfo.name;

                    ComponentName componentName = new ComponentName(packageName,classString);
                    final Intent intent= new Intent();
                    //通过Intent设置主键
                    intent.setComponent(componentName);
                    startActivity(intent);
            }
        });

        /**
         * 长按时候
         */
        app_list_view.setOnItemLongClickListener(new AdapterView.OnItemLongClickListener() {
            @Override
            public boolean onItemLongClick(AdapterView<?> parent, View view, int position, long id) {
                Toast.makeText(MainActivity.this, "长按", Toast.LENGTH_SHORT).show();
                return false;
            }
        });
    }

    /**
     * 获取所有的用户信息
     * @return
     */
    private List<ResolveInfo> getAppInfos(){
        Intent intent = new Intent(Intent.ACTION_MAIN,null);
        intent.addCategory(Intent.CATEGORY_LAUNCHER);
        return getPackageManager().queryIntentActivities(intent,0);
    }
    /**
     * 定义适配器操作数据
     */
    public class AppListAdapter extends BaseAdapter{
        List<ResolveInfo> mAppInfo;
        public AppListAdapter(List<ResolveInfo> appName){
            mAppInfo = appName;
        }

        @Override
        public int getCount() {
            //有多少条数据
            return mAppInfo.size();
        }

        @Override
        public Object getItem(int position) {
            //获取当前position位置的这一条
            return mAppInfo.get(position);
        }

        @Override
        public long getItemId(int position) {
            //获取当前position位置的这一条的ID
            return position;
        }

        @Override
        public View getView(final int position, View convertView, ViewGroup parent) {
            //处理 view--data 填充数据的一个过程
            LayoutInflater layoutInflater = (LayoutInflater) getSystemService(Context.LAYOUT_INFLATER_SERVICE);
            convertView = layoutInflater.inflate(R.layout.item_app_list,null);
            if(convertView != null){
                ImageView appIconImageView = (ImageView)convertView.findViewById(R.id.app_icon_image_view);
                TextView appNameTextView = (TextView) convertView.findViewById(R.id.app_name_text_view);

                appNameTextView.setText(mAppInfo.get(position).activityInfo.loadLabel(getPackageManager()));
                appIconImageView.setImageDrawable(mAppInfo.get(position).activityInfo.loadIcon(getPackageManager()));
            }
//            //为点击的条目设置点击事件，在getView内部设置点击事件的方法
//            convertView.setOnClickListener(new View.OnClickListener() {
//                @Override
//                public void onClick(View v) {
//                    //拿到应用的包名
//                    String packageName = mAppInfo.get(position).activityInfo.packageName;
//                    //拿到主要的类名
//                    String classString = mAppInfo.get(position).activityInfo.name;
//
//                    ComponentName componentName = new ComponentName(packageName,classString);
//                    final Intent intent= new Intent();
//                    //通过Intent设置主键
//                    intent.setComponent(componentName);
//                    startActivity(intent);
//                }
//            });
            return convertView;
        }
    }
}

MainActivity.java

增加ViewHolder优化后，修改部分的代码如下：

MainActivity.java

        @Override
        public View getView(final int position, View convertView, ViewGroup parent) {
            ViewHolder viewHolder =new ViewHolder();
            //处理 view--data 填充数据的一个过程
            if(convertView != null) {
                //减少了每次都解析Layout转化为View，和findViewById查找的消耗
                LayoutInflater layoutInflater = (LayoutInflater) getSystemService(Context.LAYOUT_INFLATER_SERVICE);
                convertView = layoutInflater.inflate(R.layout.item_app_list, null);

                viewHolder.mAppIconImageView = (ImageView)convertView.findViewById(R.id.app_icon_image_view);
                viewHolder.mAppNameTextView = (TextView) convertView.findViewById(R.id.app_name_text_view);

                convertView.setTag(viewHolder);
            }else{
                viewHolder = (ViewHolder)convertView.getTag();
            }
            
            viewHolder.mAppIconImageView.setImageDrawable(mAppInfo.get(position).activityInfo.loadIcon(getPackageManager()));
            viewHolder.mAppNameTextView.setText(mAppInfo.get(position).activityInfo.loadLabel(getPackageManager()));
            return convertView;
        }
        public class ViewHolder{
            public ImageView mAppIconImageView;
            public TextView mAppNameTextView;
        }

完整代码如下：

MainActivity.java

package com.administrator.listviewdemo;

import android.content.ComponentName;
import android.content.Context;
import android.content.Intent;
import android.content.pm.ComponentInfo;
import android.content.pm.ResolveInfo;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.AdapterView;
import android.widget.BaseAdapter;
import android.widget.ImageView;
import android.widget.ListView;
import android.widget.TextView;
import android.widget.Toast;

import java.util.ArrayList;
import java.util.List;

public class MainActivity extends AppCompatActivity {

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

        ListView app_list_view = (ListView)findViewById(R.id.app_list_view);


        //添加标题的headerView
        //解析LayoutInflater
        LayoutInflater layoutInflater = (LayoutInflater)getSystemService(Context.LAYOUT_INFLATER_SERVICE);
        View headerView = layoutInflater.inflate(R.layout.header_list,null);
        app_list_view.addHeaderView(headerView);


        final List<ResolveInfo> appInfos = getAppInfos();
        app_list_view.setAdapter(new AppListAdapter(getAppInfos()));


        /**
         * ListView在外面调用的方法
         */
        app_list_view.setOnItemClickListener(new AdapterView.OnItemClickListener() {
            @Override
            public void onItemClick(AdapterView<?> parent, View view, int position, long id) {
                    //拿到应用的包名
                    String packageName = appInfos.get(position).activityInfo.packageName;
                    //拿到主要的类名
                    String classString = appInfos.get(position).activityInfo.name;

                    ComponentName componentName = new ComponentName(packageName,classString);
                    final Intent intent= new Intent();
                    //通过Intent设置主键
                    intent.setComponent(componentName);
                    startActivity(intent);
            }
        });

        /**
         * 长按时候
         */
        app_list_view.setOnItemLongClickListener(new AdapterView.OnItemLongClickListener() {
            @Override
            public boolean onItemLongClick(AdapterView<?> parent, View view, int position, long id) {
                Toast.makeText(MainActivity.this, "长按", Toast.LENGTH_SHORT).show();
                return false;
            }
        });
    }

    /**
     * 获取所有的用户信息
     * @return
     */
    private List<ResolveInfo> getAppInfos(){
        Intent intent = new Intent(Intent.ACTION_MAIN,null);
        intent.addCategory(Intent.CATEGORY_LAUNCHER);
        return getPackageManager().queryIntentActivities(intent,0);
    }
    /**
     * 定义适配器操作数据
     */
    public class AppListAdapter extends BaseAdapter{
        List<ResolveInfo> mAppInfo;
        public AppListAdapter(List<ResolveInfo> appName){
            mAppInfo = appName;
        }

        @Override
        public int getCount() {
            //有多少条数据
            return mAppInfo.size();
        }

        @Override
        public Object getItem(int position) {
            //获取当前position位置的这一条
            return mAppInfo.get(position);
        }

        @Override
        public long getItemId(int position) {
            //获取当前position位置的这一条的ID
            return position;
        }

        @Override
        public View getView(final int position, View convertView, ViewGroup parent) {
            ViewHolder viewHolder =new ViewHolder();
            //处理 view--data 填充数据的一个过程
            if(convertView != null) {
                //减少了每次都解析Layout转化为View，和findViewById查找的消耗
                LayoutInflater layoutInflater = (LayoutInflater) getSystemService(Context.LAYOUT_INFLATER_SERVICE);
                convertView = layoutInflater.inflate(R.layout.item_app_list, null);

                viewHolder.mAppIconImageView = (ImageView)convertView.findViewById(R.id.app_icon_image_view);
                viewHolder.mAppNameTextView = (TextView) convertView.findViewById(R.id.app_name_text_view);

                convertView.setTag(viewHolder);
            }else{
                viewHolder = (ViewHolder)convertView.getTag();
            }

            viewHolder.mAppIconImageView.setImageDrawable(mAppInfo.get(position).activityInfo.loadIcon(getPackageManager()));
            viewHolder.mAppNameTextView.setText(mAppInfo.get(position).activityInfo.loadLabel(getPackageManager()));
            return convertView;
        }
        public class ViewHolder{
            public ImageView mAppIconImageView;
            public TextView mAppNameTextView;
        }
    }
}






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