即使正确调用setResult（），也要在onActivityResult（）中获得RESULT_CANCELED

Question

ActivityA是 singleTask 活动，可以通过onNewIntent()接收图片。 ActivityA使用startActivityForResult()启动另一项活动：ActivityB。 ActivityB（ singleTop ）有一个按钮：按下时，它会调用setResult()。一切都有效，除了一种情况：按下ActivityB按钮后，回家，打开图库并与ActivityA共享图像。会发生的是调用方法onActivityResult()，但意图数据为null且resultCode为 RESULT_CANCELED 。在文档中，我们读到：＆＃34;如果活动明确返回，那么resultCode将是 RESULT_CANCELED ，没有返回任何结果，或者在操作过程中崩溃了＃34;这不是我们的情况。为什么结果会丢失？

ActivityA

package com.test.test2;

import android.content.Intent;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.util.Log;
import android.view.View;

public class MainActivity extends AppCompatActivity implements View.OnClickListener
{
    private final static int ACTIVITY2_CODE = 0;


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


    @Override
    public void onClick(View v)
    {
        int     id = v.getId();

        if ( id == R.id.floatingActionButton )
        {
            Intent intent = new Intent();
            intent.setClass( this, Activity2.class );
            startActivityForResult( intent, ACTIVITY2_CODE );
        }

    }

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

        if ( requestCode == ACTIVITY2_CODE )
        {
            if ( data != null )
            {
                String test_str = data.getStringExtra("test_str" );
                Log.i( "MainActivity", ".onActivityResult(): test_str = " + test_str );
            }
        }
        else
        {
            super.onActivityResult( requestCode, resultCode, data );
        }

    }


    @Override
    public void onNewIntent ( Intent intent )
    {
        super.onNewIntent( intent );
        setIntent( intent );
        // ......
    }



    @Override
    public void onSaveInstanceState ( Bundle outState )
    {
        super.onSaveInstanceState( outState );
    }

}

ActivityB

package com.test.test2;

import android.content.Intent;
import android.os.Bundle;
import android.support.design.widget.FloatingActionButton;
import android.support.design.widget.Snackbar;
import android.support.v7.app.AppCompatActivity;
import android.support.v7.widget.Toolbar;
import android.view.View;

public class Activity2 extends AppCompatActivity {

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main2);
        Toolbar toolbar = (Toolbar) findViewById(R.id.toolbar);
        setSupportActionBar(toolbar);

        FloatingActionButton fab = (FloatingActionButton) findViewById(R.id.fab);
        fab.setOnClickListener(new View.OnClickListener()
        {
            @Override
            public void onClick(View view)
            {
                Intent purchases_intent = new Intent();
                purchases_intent.putExtra( "test_str", "ciaoooooo" );
                setResult( RESULT_OK, purchases_intent );

                Snackbar.make(view, "Replace with your own action", Snackbar.LENGTH_LONG)
                        .setAction("Action", null).show();
            }
        });
    }

}

AndroidManifest

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
    package="com.test.test2">

    <application
        android:allowBackup="true"
        android:icon="@mipmap/ic_launcher"
        android:label="@string/app_name"
        android:roundIcon="@mipmap/ic_launcher_round"
        android:supportsRtl="true"
        android:theme="@style/AppTheme">
        <activity
            android:name=".MainActivity"
            android:launchMode="singleTask"
            >
            <intent-filter>
                <action android:name="android.intent.action.MAIN" />

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

                <action android:name="android.intent.action.VIEW" />
                <action android:name="android.intent.action.EDIT" />
                <action android:name="android.intent.action.SEND" />

                <category android:name="android.intent.category.DEFAULT" />

                <data android:mimeType="image/*" />
            </intent-filter>
        </activity>
        <activity
            android:name=".Activity2"
            android:label="@string/title_activity_main2"
            android:theme="@style/AppTheme.NoActionBar"
            android:launchMode="singleTop"
            ></activity>
    </application>

</manifest>