<?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=".CreateMessageActivity">

    <LinearLayout
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:orientation="vertical">

        <EditText
            android:id="@+id/input"
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:ems="10"
            android:hint="@string/hint"
            android:inputType="textPersonName"
            android:textSize="30sp"/>

        <Button
            android:id="@+id/button"
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:onClick="onSendMessage"
            android:text="@string/send"
            android:textSize="30sp"
            />

    </LinearLayout>
</androidx.constraintlayout.widget.ConstraintLayout>

<?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"
    app:layout_constraintRight_toRightOf="parent"
    tools:context=".ReceiveMessageActivity">

    <TextView
        android:id="@+id/output"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="2nd Activity"
        android:textSize="34sp"
        app:layout_constraintLeft_toLeftOf="parent"
        app:layout_constraintRight_toRightOf="parent"
        app:layout_constraintTop_toTopOf="parent" />
</androidx.constr

<resources>
    <string name="app_name">Messager</string>
    <string name="send">Send Message</string>
    <string name="hint">Enter a message</string>
    <string name="choser">Send Message via ...</string>
</resources>

public class CreateMessageActivity extends AppCompatActivity {

    //定義常量，作為消息的key
    public static final String MESSAGE_KEY="szst.it.ping.messager";

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

    public void onSendMessage(View Button){
        //獲得編輯框引用
        EditText editText = findViewById(R.id.input);
        //取出編輯框文字
        String message = editText.getText().toString();

        //Intent是Android中的信使，新建Intent打開(kāi)，設(shè)置收件Activity為ReceiveMessageActivity
        Intent intent = new Intent(this,ReceiveMessageActivity.class) ;
        //在intent中附加消息
        intent.putExtra(MESSAGE_KEY,message);
        //向Android發(fā)出請(qǐng)求
        startActivity(intent);

    }
}

public class ReceiveMessageActivity extends AppCompatActivity {

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

        //獲得intent的引用
        Intent intent = getIntent();

        //根據(jù)key取出value
        String message = intent.getStringExtra(CreateMessageActivity.MESSAGE_KEY);

        //獲得文本框內(nèi)容，設(shè)置文字
        TextView textView = findViewById(R.id.output);
        textView.setText(message);
    }
}

public class CreateMessageActivity extends AppCompatActivity {

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

    public void onSendMessage(View Button){
        //獲得編輯框引用
        EditText editText = findViewById(R.id.input);
        //取出編輯框文字
        String message = editText.getText().toString();

        //使用new Intent(Intent.ACTION_SEND)替換new Intent(this, ReceiveMessageActivity.class)，不知道其它App中的類(lèi)名
        Intent intent = new Intent(Intent.ACTION_SEND);
        //設(shè)置消息類(lèi)型為純文本，系統(tǒng)不會(huì)對(duì)消息進(jìn)行處理
        intent.setType("text/plain");
        //向Intent添加附加信息
        intent.putExtra(Intent.EXTRA_TEXT,message);

        //自定義選擇對(duì)話(huà)框
        String chooserTitle = getString(R.string.choser);
        Intent chosenIntent = Intent.createChooser(intent, chooserTitle);

        startActivity(chosenIntent) ;
    }
}