SubActivity在另一个SubActibity中

Question

我正在开发一个mediaPlayer应用程序，我正在使用ListViews作为播放列表。我有一个包含mediaPlayer的主要活动，当用户单击播放列表按钮时，ArtistActivity启动，用户可以从其中启动SongActivity。我看过许多教程和例子，但出于某种原因，SongActivity将"0“传递回主要活动，并使用歌曲URL在ArrayList中播放第一首曲目。任何帮助都将不胜感激。请帮帮忙。谢谢。

MainActivity:

    btnPlaylist.setOnClickListener(new View.OnClickListener() {


        public void onClick(View arg0) {
            Intent i = new  Intent(getApplicationContext(),ArtistActivity.class);
            startActivityForResult(i, 100);

        }
    });

}


protected void onActivityResult(int requestCode,
        int resultCode, Intent data) {
    super.onActivityResult(requestCode, resultCode, data);
    if(resultCode == 50)
    {

        currentSongIndex = data.getExtras().getInt("songIndexArtist");

        songIndex = currentSongIndex;

        // play selected song
        playSong(currentSongIndex);

        // Displaying Song title
        String songTitle =
  songsList.get(currentSongIndex).get("songTitle");
        songTitleLabel.setText(songTitle);

    }

ArtistActivity:

lv.setOnItemClickListener(new OnItemClickListener() {

        public void onItemClick(AdapterView<?> parent, View view,
                int position, long id) {

            //int artistIndex = position;

            // Starting new intent
            Intent in2 = new Intent(getApplicationContext(),SongActivity.class);

            startActivityForResult(in2,100);

            setResult(100,in2);

            in2.putExtra("songIndexArtist", songIndexArtist);

            finish();

        }
    });
}
protected void onActivityResult(int requestCode,
        int resultCode, Intent data) {
    super.onActivityResult(requestCode, resultCode, data);
        if(resultCode == 50)
    {

        songIndexArtist = data.getExtras().getInt("songIndex");

    }

}

SongActivity:

lv.setOnItemClickListener(new OnItemClickListener() {

        public void onItemClick(AdapterView<?> parent, View view,
                int position, long id) {


            Toast.makeText(getApplicationContext(), "DOWNLOADING, PLEASE WAIT", Toast.LENGTH_LONG).show(); 

            // getting listitem index
            int songIndex = position;

            // Starting new intent
            Intent in3 = new Intent(getApplicationContext(),
                    AndroidBuildingMusicPlayerActivity.class);

            // Sending songIndex to PlayerActivity
            in3.putExtra("songIndex", songIndex);

            setResult(50,in3);

            // Closing PlayListView
            finish();
        }
    });
}

Answer 1

你把requestCode和resultCode混在一起。resultCode应该是预定义的常量RESULT_CANCELED、RESULT_OK、RESULT_FIRST_USER等。requestCode是您的唯一值- 50、100等。

而且，在相同的活动中，requestCode在startActivityForResult调用中和onActivityResult处理程序中应该是相同的。

例如，在SongActivity中，您应该调用：

setResult(RESULT_OK, in3);

在ArtistActivity中，您应该调用：

startActivityForResult(in2, 50);

因为ArtistActivity中的onActivityResult正在等待代码50。

lv.setOnItemClickListener(new OnItemClickListener() {
        public void onItemClick(AdapterView<?> parent, View view,
                int position, long id) {
            Intent in2 = new Intent(getApplicationContext(), SongActivity.class);

            // Starting SongActivity and wait for results with requestCode 50
            startActivityForResult(in2, 50);
        }
    });
}

protected void onActivityResult(int requestCode,
        int resultCode, Intent data) {
    super.onActivityResult(requestCode, resultCode, data);
    if(requestCode == 50 && resultCode == RESULT_OK)
    {
        // get results from SongActivity (requestCode = 50)
        songIndexArtist = data.getExtras().getInt("songIndex");

        // now pass the same data into MainActivity
        Intent result = new Intent();
        result.putExtra("songIndexArtist", songIndexArtist);
        setResult(RESULT_OK, result);
        finish();
    }
}

请注意，我将resultCode替换为requestCode。

您应该以类似的方式修复MainActivity。

您还可以使用标志；有一个相关的所以问题和一个很好地解释了这面旗帜 (以及其他标志)。如果您在没有任何处理的情况下通过中间活动传递结果，则该标志是有用的。