FLAG_ACTIVITY_FORWARD_RESULT的使用

分类：Android, Java 阅读 (1,354)

12月 102019

转载请注明原文地址：http://bcoder.com/java/use-of-flag_activity_forward_result

这几天看安卓系统源码的时候，遇到FLAG_ACTIVITY_FORWARD_RESULT，用于跨Activity传递ActivityResult

记得有一次面试还有面试官问到这个问题，当时还以为是说要用eventbus或者本地广播

我们先用一个图片看看这个标志的作用

下面看看三个Activity的代码

ActivityA的代码

public class AActivity extends AppCompatActivity {
    public static final int REQCODE_TEST = 10;

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

    }

    @Override
    protected void onActivityResult(int requestCode, int resultCode, @Nullable Intent data) {
        super.onActivityResult(requestCode, resultCode, data);
        String toastStr = "onActivityResult, " + this.getClass().getName()
                + ", RequestCode: " + requestCode;
        if(data != null && data.hasExtra("key")){
            toastStr += "，返回key值：" + data.getStringExtra("key");
        }
        Toast.makeText(this,  toastStr, Toast.LENGTH_SHORT).show();
    }

    public void onButton1Click(View view) {
        Intent intent = new Intent(this, BActivity.class);
        startActivityForResult(intent, REQCODE_TEST);
    }
}

public class AActivity extends AppCompatActivity {

public static final int REQCODE_TEST = 10;

@Override

protected void onCreate(Bundle savedInstanceState) {

super.onCreate(savedInstanceState);

setContentView(R.layout.activity_main);

}

@Override

protected void onActivityResult(int requestCode, int resultCode, @Nullable Intent data) {

super.onActivityResult(requestCode, resultCode, data);

String toastStr = "onActivityResult, " + this.getClass().getName()

+ ", RequestCode: " + requestCode;

if(data != null && data.hasExtra("key")){

toastStr += "，返回key值：" + data.getStringExtra("key");

}

Toast.makeText(this, toastStr, Toast.LENGTH_SHORT).show();

}

public void onButton1Click(View view) {

Intent intent = new Intent(this, BActivity.class);

startActivityForResult(intent, REQCODE_TEST);

}

ActivityB的代码

public class BActivity extends AppCompatActivity {

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

    }

    @Override
    protected void onActivityResult(int requestCode, int resultCode, @Nullable Intent data) {
        super.onActivityResult(requestCode, resultCode, data);
        Toast.makeText(this, "onActivityResult, " + this.getClass().getName() + ", " + requestCode, Toast.LENGTH_SHORT).show();
    }

    public void onButton2Click(View view) {
        Intent intent = new Intent(this, CActivity.class);
        intent.setFlags(Intent.FLAG_ACTIVITY_FORWARD_RESULT);
        startActivity(intent);
//        startActivityForResult(intent, 0); //使用FLAG_ACTIVITY_FORWARD_RESULT标志就不能再使用startActivityForResult
    }
}

public class BActivity extends AppCompatActivity {

@Override

protected void onCreate(Bundle savedInstanceState) {

super.onCreate(savedInstanceState);

setContentView(R.layout.activity_b);

}

@Override

protected void onActivityResult(int requestCode, int resultCode, @Nullable Intent data) {

super.onActivityResult(requestCode, resultCode, data);

Toast.makeText(this, "onActivityResult, " + this.getClass().getName() + ", " + requestCode, Toast.LENGTH_SHORT).show();

}

public void onButton2Click(View view) {

Intent intent = new Intent(this, CActivity.class);

intent.setFlags(Intent.FLAG_ACTIVITY_FORWARD_RESULT);

startActivity(intent);

// startActivityForResult(intent, 0); //使用FLAG_ACTIVITY_FORWARD_RESULT标志就不能再使用startActivityForResult

}

ActivityC的代码

public class CActivity extends AppCompatActivity {

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

    @Override
    public void finish() {
        Intent resultIntent = new Intent();
        resultIntent.putExtra("key", "Value_C");
        setResult(AActivity.REQCODE_TEST, resultIntent);
        super.finish();
    }

}

public class CActivity extends AppCompatActivity {

@Override

protected void onCreate(Bundle savedInstanceState) {

super.onCreate(savedInstanceState);

setContentView(R.layout.activity_c);

}

@Override

public void finish() {

Intent resultIntent = new Intent();

resultIntent.putExtra("key", "Value_C");

setResult(AActivity.REQCODE_TEST, resultIntent);

super.finish();

}

注意事项：

1.如果intent中设置了FLAG_ACTIVITY_FORWARD_RESULT就不能再使用startActivityForResult打开新的Activity了

2.setResult必须在super.finish()之前调用

3.这个标志是否适合于更多层Activity的转发？可以

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