Java 我正在使用碎片，当我快速按下后退按钮时，应用程序崩溃。这是随机发生的
我使用的是碎片，当我快速按下后退按钮时，android应用程序崩溃了。这是随机发生的，下面是java代码：Java 我正在使用碎片，当我快速按下后退按钮时，应用程序崩溃。这是随机发生的,java,android,fragment,Java,Android,Fragment,我使用的是碎片，当我快速按下后退按钮时，android应用程序崩溃了。这是随机发生的，下面是java代码： public class PlayerFragment extends Fragment { List<County> feeds; String action = "counties"; private static MediaPlayer mMediaPlayer; TextView descr; TextView feed_id;
public class PlayerFragment extends Fragment {
List<County> feeds;
String action = "counties";
private static MediaPlayer mMediaPlayer;
TextView descr;
TextView feed_id;
TextView status;
TextView listeners;
TextView genre;
TextView bitrate;
private static Button switchButton;
private AdView mAdView;
InterstitialAd mInterstitialAd;
public PlayerFragment() {
// Required empty public constructor
}
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
}
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
View rootView = inflater.inflate(R.layout.fragment_player, container, false);
//view called and initialized
initView(rootView);
updateView();
AdRequest adRequest = new AdRequest.Builder()
.build();
mAdView.loadAd(adRequest);
// set the ad unit ID
mInterstitialAd.setAdUnitId(getString(R.string.interstitial_full_screen));
// Load ads into Interstitial Ads
mInterstitialAd.loadAd(adRequest);
mInterstitialAd.setAdListener(new AdListener() {
public void onAdLoaded() {
showInterstitial();
}
});
final Retrofit.Builder builder = new Retrofit.Builder()
.baseUrl(RadioApiClient.BASE_URL)
.addConverterFactory(GsonConverterFactory.create());
Retrofit retrofit = builder.build();
RadioApiClient client = retrofit.create(RadioApiClient.class);
Call<Counties> call = client.getCounties(action,
BrowseStateFragment.stateId,
RadioApiClient.JSON_RESPONSE,
RadioApiClient.API_KEY);
Log.d("Accessing url", client.getCounties(action, BrowseStateFragment.stateId,
RadioApiClient.JSON_RESPONSE,
RadioApiClient.API_KEY).request().url().toString());
call.enqueue(new Callback<Counties>() {
@Override
public void onResponse(Call<Counties> call, Response<Counties> response) {
feeds = response.body().getCounties();
AudioManager amanager = (AudioManager) getActivity().getSystemService(Context.AUDIO_SERVICE);
int maxVolume = amanager.getStreamMaxVolume(AudioManager.STREAM_ALARM);
amanager.setStreamVolume(AudioManager.STREAM_ALARM, maxVolume, 0);
mMediaPlayer = new MediaPlayer();
mMediaPlayer.setAudioStreamType(AudioManager.STREAM_MUSIC);
mMediaPlayer.setOnPreparedListener(new MediaPlayer.OnPreparedListener() {
@Override
public void onPrepared(MediaPlayer mp) {
togglePlayPause();
}
});
String station = BrowseFeedsFragment.station;
Toast.makeText(getActivity(), "Setting radio", Toast.LENGTH_LONG).show();
if (mMediaPlayer.isPlaying()) {
mMediaPlayer.stop();
Toast.makeText(getActivity(), "stopping radio", Toast.LENGTH_LONG).show();
mMediaPlayer.reset();
Toast.makeText(getActivity(), "resetting radio", Toast.LENGTH_LONG).show();
}
try {
Toast.makeText(getActivity(), "Trying to play ", Toast.LENGTH_LONG).show();
mMediaPlayer.setDataSource(station);
mMediaPlayer.prepareAsync();
mMediaPlayer.start();
showInterstitial();
Toast.makeText(getActivity(), "playing", Toast.LENGTH_LONG).show();
} catch (IOException e) {
e.printStackTrace();
}
}
@Override
public void onFailure(Call<Counties> call, Throwable t) {
Log.d("no success", "" + "onfailure");
t.printStackTrace();
}
});
// Inflate the layout for this fragment
return rootView;
}
@Override
public void onAttach(Activity activity) {
super.onAttach(activity);
}
@Override
public void onPause() {
if (mAdView != null) {
mAdView.pause();
}
super.onPause();
}
@Override
public void onResume() {
super.onResume();
if (mAdView != null) {
mAdView.resume();
showInterstitial();
}
}
@Override
public void onDestroy() {
if (mAdView != null) {
mAdView.destroy();
}
super.onDestroy();
}
@Override
public void onDetach() {
super.onDetach();
}
private void togglePlayPause() {
if (mMediaPlayer.isPlaying()) {
mMediaPlayer.pause();
switchButton.setText("Play");
Toast.makeText(getActivity(), "Paused", Toast.LENGTH_LONG).show();
} else {
mMediaPlayer.start();
switchButton.setText("Pause");
Toast.makeText(getActivity(), "Playing", Toast.LENGTH_LONG).show();
}
}
private void showInterstitial() {
if (mInterstitialAd.isLoaded()) {
mInterstitialAd.show();
}
}
public void initView(View rootView) {
descr = (TextView) rootView.findViewById(R.id.descr);
feed_id = (TextView) rootView.findViewById(R.id.feed_id);
status = (TextView) rootView.findViewById(R.id.status);
listeners = (TextView) rootView.findViewById(R.id.listeners);
genre = (TextView) rootView.findViewById(R.id.genre);
bitrate = (TextView) rootView.findViewById(R.id.bitrate);
switchButton = (Button) rootView.findViewById(R.id.switchButton);
mAdView = (AdView) rootView.findViewById(R.id.adView);
mInterstitialAd = new InterstitialAd(getActivity());
}
public void updateView() {
//update views
descr.setText("Description: " + BrowseFeedsFragment.descr);
feed_id.setText("Feed Id: " + BrowseFeedsFragment.feed_id);
if (BrowseFeedsFragment.status == "1") {
status.setText("Status: " + "Live Streaming Active");
} else {
status.setText("Status: " + "Live Streaming Offline");
}
listeners.setText("Listerners: " + BrowseFeedsFragment.listeners);
genre.setText("Genre: " + BrowseFeedsFragment.genre);
bitrate.setText("Bitrate: " + BrowseFeedsFragment.bitrate + "KBPS");
Log.d("Success", "" + "Update Success");
//event handling
switchButton.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View view) {
togglePlayPause();
}
});
}
}
> FATAL EXCEPTION: main
> Process: com.kwawannan.policedispatchlivescanner, PID: 27704
> java.lang.NullPointerException: Attempt to invoke virtual method 'java.lang.String android.content.Context.getPackageName()' on a null
> object reference
> at android.widget.Toast.<init>(Toast.java:103)
> at android.widget.Toast.makeText(Toast.java:256)
> at com.kwawannan.policedispatchlivescanner.activity.PlayerFragment.togglePlayPause(PlayerFragment.java:208)
> at com.kwawannan.policedispatchlivescanner.activity.PlayerFragment.access$200(PlayerFragment.java:36)
> at com.kwawannan.policedispatchlivescanner.activity.PlayerFragment$2$1.onPrepared(PlayerFragment.java:123)
> at android.media.MediaPlayer$EventHandler.handleMessage(MediaPlayer.java:2872)
> at android.os.Handler.dispatchMessage(Handler.java:102)
> at android.os.Looper.loop(Looper.java:154)
> at android.app.ActivityThread.main(ActivityThread.java:6119)
> at java.lang.reflect.Method.invoke(Native Method)
> at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:886)
> at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:776)
com.kwawannan.policedispatchlivescanner, PID: 27704 java.lang.NullPointerException: Attempt to invoke virtual method 'java.lang.String android.content.Context.getPackageName()' on a null object reference at android.widget.Toast.(Toast.java:103)
Toast.makeText(getContext(), "msg text", Toast.LENGTH_LONG).show();
更改切换方法，如下所示：
private void togglePlayPause() {
Activity activity = getActivity();
if (mMediaPlayer!=null && activity!=null) {
if (mMediaPlayer.isPlaying()) {
mMediaPlayer.pause();
switchButton.setText("Play");
Toast.makeText(activity, "Paused", Toast.LENGTH_LONG).show();
} else {
mMediaPlayer.start();
switchButton.setText("Pause");
Toast.makeText(activity, "Playing", Toast.LENGTH_LONG).show();
}
}
}
我希望这将对您有所帮助。如何使用call.cancel，call在我的代码中未知在onCreateView中您正在创建call=client.getCountie。。。只需将其设为类成员，这样您就可以在调用call后仍能访问它。取消对空对象引用的“java.lang.String android.content.Context.getPackageName”，在com.kwawannan.policydispatchlivescanner.activity.PlayerFragment.togglePlayPausePlayerFragment.java:210在com.kwawannan.policydispatchLiveScanner.activity.PlayerFragment.access$200PlayerFragment.java:36在com.kwawannan.policydispatchLiveScanner.activity.PlayerFragment$2$1.onPreparedPlayerFragment.java:124可能是它的副本-您正在向某个具有无效上下文的地方显示toast我应该使用什么上下文？