Android registerForActivityResult新用法实现两个Activity间数据传递

我们来详细讲解一下如何使用Android registerForActivityResult新用法实现两个Activity间数据传递。

什么是registerForActivityResult

registerForActivityResult是Android个10.0之后新增的 API，可以简化 startActivityForResult 的操作，并且更加灵活。通过 registerForActivityResult 可以申请权限、获取图片、视频，等等。

How-To

要使用registerForActivityResult来实现两个Activity间数据传递，我们需要以下几个步骤：

步骤一：创建打开目标Activity的Intent

在目标Activity中，我们需要使用Intent的putExtra()命令在Intent中添加要传递的数据。例如，在MainActivity中打开目标Activity，并将数据传到目标Activity：

private final ActivityResultLauncher<Intent> mStartForResult = registerForActivityResult(new ActivityResultContracts.StartActivityForResult(), result -> {
    if (result.getResultCode() == Activity.RESULT_OK) {
        Intent intent = result.getData();
        //处理拿到的数据
    }
});

Intent intent = new Intent(MainActivity.this, TargetActivity.class);
intent.putExtra("message", "Hello World!");
mStartForResult.launch(intent);

步骤二：在目标Activity中获取传递的数据

目标Activity中使用getIntent()即可取到传递的数据，例如，在目标Activity中接收来自MainActivity的数据：

String message = getIntent().getStringExtra("message");

步骤三：返回数据到MainActivity中

在目标Activity中，我们可以使用 setResult() 方法返回数据给MainActivity：

Intent intent = new Intent();
intent.putExtra("returnMessage", "Got the message, thanks!");
setResult(Activity.RESULT_OK, intent);
finish();

步骤四：在MainActivity中接收返回数据

我们可以在 onActivityResult() 中获取到返回结果：

private final ActivityResultLauncher<Intent> mStartForResult = registerForActivityResult(new ActivityResultContracts.StartActivityForResult(), result -> {
    if (result.getResultCode() == Activity.RESULT_OK) {
        Intent intent = result.getData();
        String returnMessage = intent.getStringExtra("returnMessage");
        //处理返回的数据
    }
});

示例

示例一：主Activity传递数据给目标Activity

MainActivity.java:

public class MainActivity extends AppCompatActivity {
    private Button mButton;

    private final ActivityResultLauncher<Intent> mStartForResult = registerForActivityResult(new ActivityResultContracts.StartActivityForResult(), result -> {
        if (result.getResultCode() == Activity.RESULT_OK) {
            Intent intent = result.getData();
            String returnMessage = intent.getStringExtra("returnMessage");
            Toast.makeText(this, returnMessage, Toast.LENGTH_SHORT).show();
        }
    });

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

        mButton = findViewById(R.id.button);
        mButton.setOnClickListener(view -> {
            Intent intent = new Intent(MainActivity.this, TargetActivity.class);
            intent.putExtra("message", "Hello World!");
            mStartForResult.launch(intent);
        });
    }
}

TargetActivity.java:

public class TargetActivity extends AppCompatActivity {
    private String mMessage;

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

        mMessage = getIntent().getStringExtra("message");
        TextView textView = findViewById(R.id.text_view);
        textView.setText(mMessage);
    }

    public void onClick(View view) {
        Intent intent = new Intent();
        intent.putExtra("returnMessage", "Got the message, thanks!");
        setResult(Activity.RESULT_OK, intent);
        finish();
    }
}

activity_main.xml:

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    ...
    <Button
        android:id="@+id/button"
        android:text="Start TargetActivity"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content" />
</RelativeLayout>

activity_target.xml:

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    ...
    <TextView
        android:id="@+id/text_view"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="TargetActivity"
        android:textSize="24sp"
        android:layout_centerInParent="true" />

    <Button
        android:id="@+id/button"
        android:text="Return to MainActivity"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_below="@id/text_view"
        android:layout_centerHorizontal="true"
        android:onClick="onClick" />
</RelativeLayout>

这个示例演示了如何在MainActivity中传递数据到TargetActivity，并在TargetActivity中返回数据到MainActivity。

示例二：目标Activity返回数据给MainActivity

MainActivity.java:

public class MainActivity extends AppCompatActivity {
    private Button mButton;

    private final ActivityResultLauncher<Intent> mStartForResult = registerForActivityResult(new ActivityResultContracts.StartActivityForResult(), result -> {
        if (result.getResultCode() == Activity.RESULT_OK) {
            Intent intent = result.getData();
            String returnMessage = intent.getStringExtra("returnMessage");
            Toast.makeText(this, returnMessage, Toast.LENGTH_SHORT).show();
        }
    });

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

        mButton = findViewById(R.id.button);
        mButton.setOnClickListener(view -> {
            Intent intent = new Intent(MainActivity.this, TargetActivity.class);
            mStartForResult.launch(intent);
        });
    }
}

TargetActivity.java:

public class TargetActivity extends AppCompatActivity {

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

    public void onClick(View view) {
        Intent intent = new Intent();
        intent.putExtra("returnMessage", "Got the message, thanks!");
        setResult(Activity.RESULT_OK, intent);
        finish();
    }
}

activity_main.xml:

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
        ...
        <Button
            android:id="@+id/button"
            android:text="Start TargetActivity"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content" />
    </RelativeLayout>

activity_target.xml:

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
        ...
        <Button
            android:id="@+id/button"
            android:text="Return to MainActivity"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_centerInParent="true" 
            android:onClick="onClick"/>
    </RelativeLayout>

这个示例演示了如何在TargetActivity中返回数据到MainActivity。