App-Kotlin入门到精通-启动Activity(四)

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AndroidManifest.xml注册 

......

<activity android:name=".MainActivity">
            <intent-filter>
                <action android:name="android.intent.action.MAIN" />

                <category android:name="android.intent.category.LAUNCHER" />
            </intent-filter>
</activity>

......

创建布局activity_main.xml

<?xml version="1.0" encoding="utf-8"?>
<androidx.constraintlayout.widget.ConstraintLayout
xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context=".MainActivity">

    <TextView
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="MainActivity"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintLeft_toLeftOf="parent"
        app:layout_constraintRight_toRightOf="parent"
        app:layout_constraintTop_toTopOf="parent" />

</androidx.constraintlayout.widget.ConstraintLayout>

AndroidManifest.xml注册

 <activity
            android:name=".TwoActivity"
            android:parentActivityName=".MainActivity">
            <!-- The meta-data tag is required if you support API level 15 and lower -->
            <meta-data
                android:name="android.support.PARENT_ACTIVITY"
                android:value=".MainActivity" />
        </activity>

创建activity_two.xml布局

<?xml version="1.0" encoding="utf-8"?>
<androidx.constraintlayout.widget.ConstraintLayout 
xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context=".MainActivity">

    <TextView
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="TwoActivity"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintLeft_toLeftOf="parent"
        app:layout_constraintRight_toRightOf="parent"
        app:layout_constraintTop_toTopOf="parent" />

</androidx.constraintlayout.widget.ConstraintLayout>

创建Intent-与TwoActivity建立关联

 /** Called when the user taps the Send button */
    fun sendMessage(view: View) {
        val textView = findViewById<TextView>(R.id.textView)
        val message = textView.text.toString()
        val intent = Intent(this, TwoActivity::class.java).apply {
            putExtra(EXTRA_MESSAGE, message)
        }
        startActivity(intent)
    }

修改布局activity_main.xml

<?xml version="1.0" encoding="utf-8"?>
<androidx.constraintlayout.widget.ConstraintLayout 
xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context=".MainActivity">

    <TextView
        android:id="@+id/textView"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="MainActivity"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintLeft_toLeftOf="parent"
        app:layout_constraintRight_toRightOf="parent"
        app:layout_constraintTop_toTopOf="parent" />

    <Button
        android:id="@+id/button"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:onClick="sendMessage"
        android:text="senMessage"
        tools:layout_editor_absoluteX="148dp"
        tools:layout_editor_absoluteY="444dp"
        tools:ignore="MissingConstraints" />

</androidx.constraintlayout.widget.ConstraintLayout>

 接受MainActivity传递的消息 

class TwoActivity : AppCompatActivity() {

    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.activity_two)

        // Get the Intent that started this activity and extract the string
        val message = intent.getStringExtra(EXTRA_MESSAGE)

        // Capture the layout's TextView and set the string as its text
        val textView = findViewById<TextView>(R.id.textView).apply {
            text = message
        }
    }
}

 范型 Class<T>

 fun  <T : Activity>  comToActivity(t: Class<T>,message : String) {
        val intent=Intent(this, t).apply {
            putExtra(EXTRA_MESSAGE, message)
        };
        startActivity(intent)
    }

class MainActivity : AppCompatActivity() {



    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.activity_main)
    }

    /** Called when the user taps the Send button */
    fun sendMessage(view: View) {
        val textView = findViewById<TextView>(R.id.textView)
        val message = textView.text.toString()
        comToActivity(TwoActivity::class.java,message);
    }

    fun  <T : Activity>  comToActivity(t: Class<T>,message : String) {
        val intent=Intent(this, t).apply {
            putExtra(EXTRA_MESSAGE, message)
        };
        startActivity(intent)
    }
}

正确使用 android:parentActivityName

 <activity
            android:name=".TwoActivity"
            android:parentActivityName=".MainActivity">
            <!-- The meta-data tag is required if you support API level 15 and lower -->
            <meta-data
                android:name="android.support.PARENT_ACTIVITY"
                android:value=".MainActivity" />
        </activity>

        <activity
            android:name=".ThreeActivity"
            android:parentActivityName=".MainActivity">
            <!-- The meta-data tag is required if you support API level 15 and lower -->
            <meta-data
                android:name="android.support.PARENT_ACTIVITY"
                android:value=".MainActivity" />
        </activity>

 <activity
            android:name=".TwoActivity"
            android:parentActivityName=".MainActivity">
            <!-- The meta-data tag is required if you support API level 15 and lower -->
            <meta-data
                android:name="android.support.PARENT_ACTIVITY"
                android:value=".MainActivity" />
        </activity>

        <activity
            android:name=".ThreeActivity"
            android:parentActivityName=".TwoActivity">
            <!-- The meta-data tag is required if you support API level 15 and lower -->
            <meta-data
                android:name="android.support.PARENT_ACTIVITY"
                android:value=".TwoActivity" />
        </activity>

取消导航栏默认返回图标

<activity android:name=".TwoActivity">
        </activity>

        <activity android:name=".ThreeActivity">
           
        </activity>

    

下载资源

参考:

Kotlin范型:https://www.kotlincn.net/docs/reference/generics.html

Kotlin 中的泛型介绍:https://zhuanlan.zhihu.com/p/78721880

【码上开学】Kotlin 的泛型:https://www.bilibili.com/video/av66340216/

Kotlin学习笔记：泛型:https://www.jianshu.com/p/ea7e8356a23b