我在活动之间接收意图附加信息时遇到了问题。
在我的MainActivity中,我启动一个Gallery活动来选择外部SD卡上的视频文件:
public class MainMenu extends Activity {
//Button change video
Button video_change;
//Extra for changing video content
Bundle extras;
//Intent for Gallery view activity
Intent intent;
@Override
protected void onCreate(final Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
//...
intent = new Intent(getApplicationContext(),GalleryView.class);
video_change.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
Uri mUri = null;
try {
Field mUriField = VideoView.class.getDeclaredField("mUri");
mUriField.setAccessible(true);
mUri = (Uri) mUriField.get(myVideoView);
} catch(Exception e) {
//TODO: Something here
}
String string = mUri.toString();
intent.putExtra("old_video",string);
startActivity(intent);
}
});
}
@Override
public synchronized void onResume() {
super.onResume();
if (Config.DEBUG)
Log.d(CLASS_NAME, "+ ON RESUME +");
try {
extras = intent.getExtras();
if (extras != null){
Log.d("++ ON RESUME ++","Found Extra!");
String newvideo = extras.getString("new_video");
Log.d("++ ON RESUME ++","NEW VIDEO: "+ newvideo);
Uri tempuri = Uri.parse(newvideo);
myVideoView.setVideoURI(tempuri);
}
} catch (Exception e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
View decorView = getWindow().getDecorView();
decorView.setSystemUiVisibility(View.SYSTEM_UI_FLAG_LAYOUT_STABLE
| View.SYSTEM_UI_FLAG_LAYOUT_HIDE_NAVIGATION
| View.SYSTEM_UI_FLAG_LAYOUT_FULLSCREEN
| View.SYSTEM_UI_FLAG_HIDE_NAVIGATION
| View.SYSTEM_UI_FLAG_FULLSCREEN
| View.SYSTEM_UI_FLAG_IMMERSIVE_STICKY);
}
}
然后在我的GalleryView活动中:
public class GalleryView extends Activity {
ImageView back_button;
ListView videolist;
List<String> videos = new ArrayList<String>();
private File[] videoFiles;
//private Cursor videocursor;
//private int video_column_index;
int x=0;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.gallery);
back_button = (ImageView) findViewById(R.id.back_button);
videolist = (ListView) findViewById(R.id.listview);
start_listview();
ArrayAdapter adapter = new ArrayAdapter<String>(this,R.layout.activity_listview,videos);
videolist.setAdapter(adapter);
videolist.setOnItemClickListener(new OnItemClickListener(){
@Override
public void onItemClick(AdapterView<?> adapter, View v, int position, long arg3) {
String value = (String)adapter.getItemAtPosition(position);
Log.d("VALUE: ",value);
Intent i = new Intent(getApplicationContext(),MainMenu.class);
// Send the file path
i.putExtra("new_video", value);
startActivity(i);
}
});
back_button.setOnClickListener(new OnClickListener() {
//videolist.setAdapter(new VideoAdapter(getApplicationContext()));
@Override
public void onClick(View v) {
//videolist.setOnItemClickListener(videogridlistener);
Intent intent = new Intent(getApplicationContext(),MainMenu.class);
Bundle extras = getIntent().getExtras();
String newString = extras.getString("old_video");
intent.putExtra("new_video", newString);
startActivity(intent);
}
});
}
public void start_listview() {
String path = ("/storage/extsd/Videos/");
File directory = new File(path);
videoFiles = directory.listFiles();
try {
for (File f : videoFiles) {
Log.d("FILE: ", f.toString());
String file = f.toString();
Uri tempuri = Uri.fromFile(f);
videos.add(file);
}
//Set the visibility of the progress bar to false.
findViewById(R.id.relativelayout_progress).setVisibility(View.GONE);
} catch (Exception e) {
// TODO: handle exception
}
}
}
问题是,当我返回到主菜单活动时,发现额外信息,但它是null!来自logcat的信息:
MainMenu + ON RESUME +
++ ON RESUME ++ Found Extra!
++ ON RESUME ++ NEWVIDEO: null
即使我将extras = intent.getExtras()
调用放在onCreate中,它也永远不会被调用,因为它从未通过extras != null
检查。
我的解决方法(感谢Stefan的答案)
所以我的主要问题是每当我启动新的Gallery Activity时,我的Main Activity总是被设置为后台。我的清单文件规定它会对Main Activity进行android:launchMode="singleTask"
设置。因此,当重新启动Main Activity时,由于应用程序始终在后台运行并且从未传递意图extras,因此意图从未真正传递。因此,我尝试了onNewIntent()方法调用,并在其中尝试了这段代码来接收extras,结果奏效了!再次感谢Stefan!
startActivityForResult
并在onActivityResult
中检索值。https://developer.android.com/training/basics/intents/result.html - Ken Wolf