我想将活动父级从ListActivity更改为AppCompatActivity,因为我需要使用已授予的检查权限,并且需要AppCompat,但是我的活动是ListView。我尝试了此操作,但未收到良好的效果:(
这是我的源代码(每个都有...是没有附加的代码):
public class RingtoneSelectActivity extends ListActivity {
...
@Override
public void onCreate(Bundle icicle) {
super.onCreate(icicle);
mShowAll = false;
String status = Environment.getExternalStorageState();
if (status.equals(Environment.MEDIA_MOUNTED_READ_ONLY)) {
showFinalAlert(getResources().getText(R.string.err_sdcard_readonly));
return;
}
if (status.equals(Environment.MEDIA_SHARED)) {
showFinalAlert(getResources().getText(R.string.err_sdcard_shared));
return;
}
if (!status.equals(Environment.MEDIA_MOUNTED)) {
showFinalAlert(getResources().getText(R.string.err_no_sdcard));
return;
}
Intent intent = getIntent();
mWasGetContentIntent = intent.getAction().equals(
Intent.ACTION_GET_CONTENT);
// Inflate our UI from its XML layout description.
setContentView(R.layout.media_select);
SplashHandler mHandler = new SplashHandler();
Message msg = new Message();
//Assign a unique code to the message.
//Later, this code will be used to identify the message in Handler class.
msg.what = 0;
// Send the message with a delay of 3 seconds(3000 = 3 sec).
mHandler.sendMessageDelayed(msg, 10000);
try {
mAdapter = new SimpleCursorAdapter(
this,
// Use a template that displays a text view
R.layout.media_select_row,
// Give the cursor to the list adatper
createCursor(""),
// Map from database columns...
new String[]{
MediaStore.Audio.Media.ARTIST,
MediaStore.Audio.Media.ALBUM,
MediaStore.Audio.Media.TITLE,
MediaStore.Audio.Media._ID,
MediaStore.Audio.Media._ID},
// To widget ids in the row layout...
new int[]{
R.id.row_artist,
R.id.row_album,
R.id.row_title,
R.id.row_icon,
R.id.row_options_button});
setListAdapter(mAdapter);
getListView().setItemsCanFocus(true);
// Normal click - open the editor
getListView().setOnItemClickListener(new OnItemClickListener() {
public void onItemClick(AdapterView parent,
View view,
int position,
long id) {
startRingdroidEditor();
}
});
} catch (SecurityException e) {
// No permission to retrieve audio?
Log.e("Ringtone", e.toString());
// todo error 1
} catch (IllegalArgumentException e) {
// No permission to retrieve audio?
Log.e("Ringtone", e.toString());
// todo error 2
}
mAdapter.setViewBinder(new SimpleCursorAdapter.ViewBinder() {
public boolean setViewValue(View view,
Cursor cursor,
int columnIndex) {
if (view.getId() == R.id.row_options_button) {
// Get the arrow image view and set the onClickListener to open the context menu.
ImageView iv = (ImageView) view;
iv.setOnClickListener(new View.OnClickListener() {
public void onClick(View v) {
openContextMenu(v);
}
});
return true;
} else if (view.getId() == R.id.row_icon) {
setSoundIconFromCursor((ImageView) view, cursor);
return true;
}
return false;
}
});
// Long-press opens a context menu
registerForContextMenu(getListView());
}
}
...
}
我改为::>
public class RingtoneSelectActivity extends AppCompatActivity {
但是我在这行中收到一些错误:
... setListAdapter(mAdapter); getListView().setItemsCanFocus(true); getListView().setOnItemClickListener(new OnItemClickListener() { ... }); ... registerForContextMenu(getListView());
我的错误:
如何解决该错误?
[编辑]
我的LogCat:
E/ACRA: ACRA caught a NullPointerException for ir.ari.mp3cutter java.lang.NullPointerException: Attempt to invoke virtual method 'void android.widget.SimpleCursorAdapter.changeCursor(android.database.Cursor)' on a null object reference at ir.ari.mp3cutter.RingtoneSelectActivity.refreshListView(RingtoneSelectActivity.java:621) at ir.ari.mp3cutter.RingtoneSelectActivity.onOptionsItemSelected(RingtoneSelectActivity.java:314) at android.app.Activity.onMenuItemSelected(Activity.java:2908) at com.android.internal.policy.PhoneWindow.onMenuItemSelected(PhoneWindow.java:1151) at com.android.internal.view.menu.MenuBuilder.dispatchMenuItemSelected(MenuBuilder.java:761) at com.android.internal.view.menu.MenuItemImpl.invoke(MenuItemImpl.java:152) at com.android.internal.view.menu.MenuBuilder.performItemAction(MenuBuilder.java:904) at com.android.internal.view.menu.MenuBuilder.performItemAction(MenuBuilder.java:894) at com.android.internal.view.menu.MenuPopupHelper.onItemClick(MenuPopupHelper.java:200) at android.widget.AdapterView.performItemClick(AdapterView.java:310) at android.widget.AbsListView.performItemClick(AbsListView.java:1145) at android.widget.AbsListView$PerformClick.run(AbsListView.java:3042) at android.widget.AbsListView$3.run(AbsListView.java:3879) at android.os.Handler.handleCallback(Handler.java:739) at android.os.Handler.dispatchMessage(Handler.java:95) at android.os.Looper.loop(Looper.java:148) at android.app.ActivityThread.main(ActivityThread.java:5417) at java.lang.reflect.Method.invoke(Native Method) at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:726) at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:616)
第304行至319行:
@Override public boolean onOptionsItemSelected(MenuItem item) { switch (item.getItemId()) { case R.id.action_about: RingtoneEditActivity.onAbout(this); return true; case R.id.action_record: onRecord(); return true; case R.id.action_show_all_audio: mShowAll = true; refreshListView(); return true; default: return false; } }
以及第619至622行:
private void refreshListView() { String filterStr = mFilter.getQuery().toString(); mAdapter.changeCursor(createCursor(filterStr)); }
[[注意:对不起我的讲话,因为我没有学好英语:)
我想将活动父级从ListActivity更改为AppCompatActivity,因为我需要使用已授予的检查权限,并且需要AppCompat,但是我的活动是ListView。我尝试了此操作,但是...
因此,请勿更改超类,只需使用ContextCompat.checkSelfPermission()
检查不需要的权限,然后通过ActivityCompat.requestPermissions()
请求权限,并在以下位置获得结果: