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，但没有收到很好的效果：（
这是我的源代码（每个都有...表示没有添加的代码）：
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：
- 无法解析方法'setListAdapter（android.widget.SimpleCursorAdapter）
- 无法解析方法“ getListView（）”
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行到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;
}
}
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：）