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组件通信1 获取子活动的返回值

创建Activity时实现自动注册！【Activity必须要注册才能使用】

默认 LinearLayout 布局，注意 xml 中约束布局的使用；

若需要更改线性布局只需要将标签更改为 LinearLayout 即可，记得设置线性布局的方向orientation；

activity_main1中约束布局

<?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:id="@+id/main"android:layout_width="match_parent"android:layout_height="match_parent"tools:context=".MainActivity"><Buttonandroid:layout_width="wrap_content"android:layout_height="wrap_content"android:text="登录"app:layout_constraintBottom_toBottomOf="parent"app:layout_constraintEnd_toEndOf="parent"app:layout_constraintStart_toStartOf="parent"app:layout_constraintTop_toTopOf="parent"android:id="@+id/btn_login"/><LinearLayoutandroid:layout_width="match_parent"android:layout_height="wrap_content"android:orientation="horizontal"android:gravity="center"app:layout_constraintTop_toBottomOf="@+id/btn_login"><TextViewandroid:layout_width="wrap_content"android:layout_height="wrap_content"android:text="用户名：" /><EditTextandroid:layout_width="wrap_content"android:layout_height="wrap_content"android:id="@+id/edt_name"/></LinearLayout></androidx.constraintlayout.widget.ConstraintLayout>

activity_main2中约束布局

父布局约束_LineayLayout（id值是linear）

app:layout_constraintBottom_toBottomOf="parent" 底部约束
app:layout_constraintEnd_toEndOf="parent" 右边约束
app:layout_constraintStart_toStartOf="parent" 左边约束
app:layout_constraintTop_toTopOf="parent" 顶部约束

子空间约束_Button

app:layout_constraintTop_toBottomOf="@+id/linear" 顶部添加约束到父布局控件的底部
app:layout_constraintEnd_toEndOf="@+id/linear" 右边添加约束到父布局控件右边
app:layout_constraintStart_toStartOf="@+id/linear" 左边添加约束到父布局控件左边

<?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:id="@+id/main"android:layout_width="match_parent"android:layout_height="match_parent"tools:context=".MainActivity2"><LinearLayoutandroid:id="@+id/linear"android:layout_width="match_parent"android:layout_height="wrap_content"android:gravity="center"android:orientation="horizontal"app:layout_constraintBottom_toBottomOf="parent"app:layout_constraintEnd_toEndOf="parent"app:layout_constraintStart_toStartOf="parent"app:layout_constraintTop_toTopOf="parent"><TextViewandroid:layout_width="wrap_content"android:layout_height="wrap_content"android:text="用户名：" /><EditTextandroid:id="@+id/edt_name"android:layout_width="wrap_content"android:layout_height="wrap_content" /></LinearLayout><Buttonandroid:id="@+id/btn_return"android:layout_width="wrap_content"android:layout_height="wrap_content"android:gravity="center"android:text="返回"app:layout_constraintTop_toBottomOf="@+id/linear"app:layout_constraintEnd_toEndOf="@+id/linear"app:layout_constraintStart_toStartOf="@+id/linear" />
</androidx.constraintlayout.widget.ConstraintLayout>

MainActivity.java

package com.example.exp4_2;import android.content.Intent;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.widget.EditText;import androidx.activity.EdgeToEdge;
import androidx.annotation.Nullable;
import androidx.appcompat.app.AppCompatActivity;
import androidx.core.graphics.Insets;
import androidx.core.view.ViewCompat;
import androidx.core.view.WindowInsetsCompat;public class MainActivity extends AppCompatActivity {Button btn_login;EditText edt_name;@Overrideprotected void onCreate(Bundle savedInstanceState) {super.onCreate(savedInstanceState);EdgeToEdge.enable(this);setContentView(R.layout.activity_main);ViewCompat.setOnApplyWindowInsetsListener(findViewById(R.id.main), (v, insets) -> {Insets systemBars = insets.getInsets(WindowInsetsCompat.Type.systemBars());v.setPadding(systemBars.left, systemBars.top, systemBars.right, systemBars.bottom);return insets;});btn_login = findViewById(R.id.btn_login);btn_login.setOnClickListener(new View.OnClickListener() {@Overridepublic void onClick(View view) {//显式启动Intent intent = new Intent(MainActivity.this, MainActivity2.class);//以sub_activity的方式启动子Activity//参数两个 intent int(请求码)startActivityForResult(intent,0);}});}@Overrideprotected void onActivityResult(int requestCode, int resultCode, @Nullable Intent data) {super.onActivityResult(requestCode, resultCode, data);edt_name = findViewById(R.id.edt_name);//得到返回值edt_name.setText(data.getStringExtra("name"));}
}

MainActivity2.java

package com.example.exp4_2;import android.content.Intent;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.widget.EditText;import androidx.activity.EdgeToEdge;
import androidx.appcompat.app.AppCompatActivity;
import androidx.core.graphics.Insets;
import androidx.core.view.ViewCompat;
import androidx.core.view.WindowInsetsCompat;public class MainActivity2 extends AppCompatActivity {@Overrideprotected void onCreate(Bundle savedInstanceState) {Button btn_return;EditText edt_name;super.onCreate(savedInstanceState);EdgeToEdge.enable(this);setContentView(R.layout.activity_main2);ViewCompat.setOnApplyWindowInsetsListener(findViewById(R.id.main), (v, insets) -> {Insets systemBars = insets.getInsets(WindowInsetsCompat.Type.systemBars());v.setPadding(systemBars.left, systemBars.top, systemBars.right, systemBars.bottom);return insets;});btn_return = findViewById(R.id.btn_return);edt_name = findViewById(R.id.edt_name);btn_return.setOnClickListener(new View.OnClickListener() {@Overridepublic void onClick(View view) {Intent intent = new Intent();intent.putExtra("name",edt_name.getText().toString());//将intent容器中储存的Activity的返回值作为参数传给setResult方法;setResult(0,intent);finish();}});}
}

结果

点击登录按钮进入子活动2，在子活动2中点击返回按钮，将活动2页面中的用户名作为子活动的返回信息通过 intent 传递给父活动1，并显示在父活动1中的EditText；

组件通信2

题目要求

用户点击“启动Activity1”和“启动Activity2”按钮时，程序将分别启动子SubActivity1和SubActivity2；

SubActivity1提供了一个输入框，以及“接受”和“撤销”两个按钮。如果在输入框中输入信息后点击“接受”按钮，程序会把输入框中的信息传递给其父Activity，并在父Activity的界面上显示。如果用户点击“撤销”按钮，则程序不会向父Activity传递任何信息。 SubActivity2主要是为了说明如何在父Activity中处理多个子Activity，因此仅提供了用于关闭SubActivity2的“关闭”按钮。

注意：在启动子Activity 时用的是显式启动；和隐式启动的区别在于 Intent 对象的构造形式不同；

在两个子Activity 的时候 Requestcode 和 Resultcode 的重要性；

activity_main.xml

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout 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:id="@+id/main"android:layout_width="match_parent"android:layout_height="match_parent"android:orientation="vertical"tools:context=".MainActivity"><Buttonandroid:layout_width="wrap_content"android:layout_height="wrap_content"android:text="启动Activity1"android:id="@+id/btn_1"/><Buttonandroid:layout_width="wrap_content"android:layout_height="wrap_content"android:text="启动Activity2"android:id="@+id/btn_2"/><TextViewandroid:layout_width="wrap_content"android:layout_height="wrap_content"android:id="@+id/txt_result"/>
</LinearLayout>

activity_main2.xml

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout 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:id="@+id/main"android:layout_width="match_parent"android:layout_height="match_parent"android:orientation="vertical"tools:context=".MainActivity2"><TextViewandroid:layout_width="wrap_content"android:layout_height="wrap_content"android:text="sub_activity1"/><EditTextandroid:layout_width="wrap_content"android:layout_height="wrap_content"android:id="@+id/edt_input"/><Buttonandroid:layout_width="wrap_content"android:layout_height="wrap_content"android:text="接受"android:id="@+id/btn_accept"/><Buttonandroid:layout_width="wrap_content"android:layout_height="wrap_content"android:text="撤销"android:id="@+id/btn_conceal"/>
</LinearLayout>

activity_main3.xml

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout 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:id="@+id/main"android:layout_width="match_parent"android:layout_height="match_parent"android:orientation="vertical"tools:context=".MainActivity3"><TextViewandroid:layout_width="wrap_content"android:layout_height="wrap_content"android:text="sub_activity2"/><Buttonandroid:layout_width="wrap_content"android:layout_height="wrap_content"android:text="关闭"android:id="@+id/btn_close"/>
</LinearLayout>

MainActivity.java

package com.example.exp4_3;import android.content.Intent;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.widget.TextView;import androidx.activity.EdgeToEdge;
import androidx.annotation.Nullable;
import androidx.appcompat.app.AppCompatActivity;
import androidx.core.graphics.Insets;
import androidx.core.view.ViewCompat;
import androidx.core.view.WindowInsetsCompat;public class MainActivity extends AppCompatActivity {Button btn_1,btn_2;TextView txt_result;//必须设置成final 否则switch case 报错static final int request_flag1 = 1;static final int request_flag2 = 2;@Overrideprotected void onCreate(Bundle savedInstanceState) {super.onCreate(savedInstanceState);EdgeToEdge.enable(this);setContentView(R.layout.activity_main);ViewCompat.setOnApplyWindowInsetsListener(findViewById(R.id.main), (v, insets) -> {Insets systemBars = insets.getInsets(WindowInsetsCompat.Type.systemBars());v.setPadding(systemBars.left, systemBars.top, systemBars.right, systemBars.bottom);return insets;});btn_1 = findViewById(R.id.btn_1);btn_2 = findViewById(R.id.btn_2);btn_1.setOnClickListener(new View.OnClickListener() {@Overridepublic void onClick(View view) {Intent intent = new Intent(MainActivity.this, MainActivity2.class);//参数两个 Intent 请求码requestcode-intstartActivityForResult(intent,request_flag1);}});btn_2.setOnClickListener(new View.OnClickListener() {@Overridepublic void onClick(View view) {Intent intent = new Intent(MainActivity.this, MainActivity3.class);//参数两个 Intent 请求码requestcode-intstartActivityForResult(intent,request_flag2);}});}@Overrideprotected void onActivityResult(int requestCode, int resultCode, @Nullable Intent data) {super.onActivityResult(requestCode, resultCode, data);txt_result = findViewById(R.id.txt_result);switch(requestCode){case request_flag1://判断结果码是 接受 还是 撤销if(resultCode==RESULT_OK){txt_result.setText(data.getStringExtra("name"));}else{txt_result.setText("sub_activity1返回空信息");}break;case request_flag2:txt_result.setText("sub_activity2返回空信息");break;}}
}

MainActivity2.java

package com.example.exp4_3;import android.content.Intent;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.widget.EditText;
import android.widget.TextView;import androidx.activity.EdgeToEdge;
import androidx.appcompat.app.AppCompatActivity;
import androidx.core.graphics.Insets;
import androidx.core.view.ViewCompat;
import androidx.core.view.WindowInsetsCompat;public class MainActivity2 extends AppCompatActivity {Button btn_accept,btn_conceal;EditText edt_input;@Overrideprotected void onCreate(Bundle savedInstanceState) {super.onCreate(savedInstanceState);EdgeToEdge.enable(this);setContentView(R.layout.activity_main2);ViewCompat.setOnApplyWindowInsetsListener(findViewById(R.id.main), (v, insets) -> {Insets systemBars = insets.getInsets(WindowInsetsCompat.Type.systemBars());v.setPadding(systemBars.left, systemBars.top, systemBars.right, systemBars.bottom);return insets;});btn_accept = findViewById(R.id.btn_accept);btn_conceal = findViewById(R.id.btn_conceal);edt_input = findViewById(R.id.edt_input);btn_accept.setOnClickListener(new View.OnClickListener() {@Overridepublic void onClick(View view) {//显式启动Intent intent = new Intent();intent.putExtra("name",edt_input.getText().toString());//参数两个 结果码Result_OK IntentsetResult(RESULT_OK,intent);finish();}});btn_conceal.setOnClickListener(new View.OnClickListener() {@Overridepublic void onClick(View view) {//Intent intent = new Intent();//setResult(RESULT_CANCELED,intent);//参数两个 结果码Result_CANCELED NULLsetResult(RESULT_CANCELED,null);finish();}});}
}

MainActivity3.java

package com.example.exp4_3;import android.os.Bundle;
import android.view.View;
import android.widget.Button;import androidx.activity.EdgeToEdge;
import androidx.appcompat.app.AppCompatActivity;
import androidx.core.graphics.Insets;
import androidx.core.view.ViewCompat;
import androidx.core.view.WindowInsetsCompat;public class MainActivity3 extends AppCompatActivity {Button btn_close;@Overrideprotected void onCreate(Bundle savedInstanceState) {super.onCreate(savedInstanceState);EdgeToEdge.enable(this);setContentView(R.layout.activity_main3);ViewCompat.setOnApplyWindowInsetsListener(findViewById(R.id.main), (v, insets) -> {Insets systemBars = insets.getInsets(WindowInsetsCompat.Type.systemBars());v.setPadding(systemBars.left, systemBars.top, systemBars.right, systemBars.bottom);return insets;});Button btn_close = findViewById(R.id.btn_close);btn_close.setOnClickListener(new View.OnClickListener() {@Overridepublic void onClick(View view) {setResult(RESULT_CANCELED,null);finish();}});}
}