从这个问题主题可以看出，当在模拟器上运行我的程序时，它第一次完美运行，但是当我再次运行它而没有任何更改时，它显示＆＃34;（项目名称）已停止工作。
我真的不知道如何解决这个问题，我尝试清理项目，再次构建APK，但仍然没有解决方案。
任何帮助请，将不胜感激。
这是我的代码：
public class MainActivity extends AppCompatActivity {
LocationManager locationManager;
LocationListener locationListener;
TextView latitude;
TextView longitude;
TextView accuracy;
TextView altitude;
TextView address;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
latitude = (TextView) findViewById(R.id.latitude);
longitude = (TextView) findViewById(R.id.longitude);
accuracy = (TextView) findViewById(R.id.accuracy);
altitude = (TextView) findViewById(R.id.altitude);
locationManager = (LocationManager) this.getSystemService(Context.LOCATION_SERVICE);
// Check if we already have a location access permission
if (ContextCompat.checkSelfPermission(this, Manifest.permission.ACCESS_FINE_LOCATION) != PackageManager.PERMISSION_GRANTED) {
// this mean we don't have permissions, so we need to ask for it.
ActivityCompat.requestPermissions(this, new String[]{Manifest.permission.ACCESS_FINE_LOCATION}, 1); // 1 here is some sort of id to identify this request, its called request code
} else {
// we do have permission
// 0 , 0 mean always keep track of user location changes, we can change it to be every 10 seconds or something like that.
locationManager.requestLocationUpdates(LocationManager.GPS_PROVIDER, 0, 0, locationListener);
}
locationListener = new LocationListener() {
@Override
public void onLocationChanged(Location location) {
latitude.setText("Latitude: " + location.getLatitude());
longitude.setText("Longitude: " + location.getLongitude());
accuracy.setText("Accuracy: " + location.getAccuracy());
altitude.setText("Alitiude: " + location.getAltitude());
}
@Override
public void onStatusChanged(String provider, int status, Bundle extras) {
}
@Override
public void onProviderEnabled(String provider) {
}
@Override
public void onProviderDisabled(String provider) {
}
};
}
@Override // this controls the dialog that asks user for location access permission
public void onRequestPermissionsResult(int requestCode, @NonNull String[] permissions, @NonNull int[] grantResults) {
super.onRequestPermissionsResult(requestCode, permissions, grantResults);
// check if user clicked on the dialog and choose allow.
if (grantResults.length > 0 && grantResults[0] == PackageManager.PERMISSION_GRANTED) {
// if we have permission, then update user location. we need this check to make the code run!
if (ContextCompat.checkSelfPermission(this, Manifest.permission.ACCESS_FINE_LOCATION) == PackageManager.PERMISSION_GRANTED) {
// 0 , 0 mean always keep track of user location changes, we can change it to be every 10 seconds or something like that.
locationManager.requestLocationUpdates(LocationManager.GPS_PROVIDER, 0, 0, locationListener);
}
}
}
}
即使我复制此代码并将其放入一个新项目中，它仍然可以工作，但是当我再次运行它同样的问题它不起作用。
我收到了这个错误
09-10 21：35：37.936 2588-2588 / com.example.qubayel.test2 E / AndroidRuntime：FATAL EXCEPTION：main 处理：com.example.qubayel.test2，PID：2588 java.lang.RuntimeException：无法启动活动ComponentInfo {com.example.qubayel.test2 / com.example.qubayel.test2.MainActivity}：java.lang.IllegalArgumentException：无效的侦听器：null 在android.app.ActivityThread.performLaunchActivity（ActivityThread.java:2665） 在android.app.ActivityThread.handleLaunchActivity（ActivityThread.java:2726） 在android.app.ActivityThread.-wrap12（ActivityThread.java） 在android.app.ActivityThread $ H.handleMessage（ActivityThread.java:1477） 在android.os.Handler.dispatchMessage（Handler.java:102） 在android.os.Looper.loop（Looper.java:154） 在android.app.ActivityThread.main（ActivityThread.java:6119） at java.lang.reflect.Method.invoke（Native Method） 在com.android.internal.os.ZygoteInit $ MethodAndArgsCaller.run（ZygoteInit.java:886） 在com.android.internal.os.ZygoteInit.main（ZygoteInit.java:776）
答案 0 :(得分：0)
我找到了解决方案，问题是我在定义之前使用了locationListener。在这行代码中：
// 0 , 0 mean always keep track of user location changes, we can change it to be every 10 seconds or something like that.
locationManager.requestLocationUpdates(LocationManager.GPS_PROVIDER, 0, 0, locationListener);
这个定义应该在我的locationListener调用之上：
locationListener = new LocationListener() {
@Override
public void onLocationChanged(Location location) {
latitude.setText("Latitude: " + location.getLatitude());
longitude.setText("Longitude: " + location.getLongitude());
accuracy.setText("Accuracy: " + location.getAccuracy());
altitude.setText("Alitiude: " + location.getAltitude());
}
@Override
public void onStatusChanged(String provider, int status, Bundle extras) {
}
@Override
public void onProviderEnabled(String provider) {
}
@Override
public void onProviderDisabled(String provider) {
}
};
最终代码应该是这样的：
public class MainActivity extends AppCompatActivity {
LocationManager locationManager;
LocationListener locationListener;
TextView latitude;
TextView longitude;
TextView accuracy;
TextView altitude;
TextView address;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
latitude = (TextView) findViewById(R.id.latitude);
longitude = (TextView) findViewById(R.id.longitude);
accuracy = (TextView) findViewById(R.id.accuracy);
altitude = (TextView) findViewById(R.id.altitude);
locationManager = (LocationManager) this.getSystemService(Context.LOCATION_SERVICE);
locationListener = new LocationListener() {
@Override
public void onLocationChanged(Location location) {
latitude.setText("Latitude: " + location.getLatitude());
longitude.setText("Longitude: " + location.getLongitude());
accuracy.setText("Accuracy: " + location.getAccuracy());
altitude.setText("Alitiude: " + location.getAltitude());
}
@Override
public void onStatusChanged(String provider, int status, Bundle extras) {
}
@Override
public void onProviderEnabled(String provider) {
}
@Override
public void onProviderDisabled(String provider) {
}
};
// Check if we already have a location access permission
if (ContextCompat.checkSelfPermission(this, Manifest.permission.ACCESS_FINE_LOCATION) != PackageManager.PERMISSION_GRANTED) {
// this mean we don't have permissions, so we need to ask for it.
ActivityCompat.requestPermissions(this, new String[]{Manifest.permission.ACCESS_FINE_LOCATION}, 1); // 1 here is some sort of id to identify this request, its called request code
} else {
// we do have permission
// 0 , 0 mean always keep track of user location changes, we can change it to be every 10 seconds or something like that.
locationManager.requestLocationUpdates(LocationManager.GPS_PROVIDER, 0, 0, locationListener);
}
}
@Override // this controls the dialog that asks user for location access permission
public void onRequestPermissionsResult(int requestCode, @NonNull String[] permissions, @NonNull int[] grantResults) {
super.onRequestPermissionsResult(requestCode, permissions, grantResults);
// check if user clicked on the dialog and choose allow.
if (grantResults.length > 0 && grantResults[0] == PackageManager.PERMISSION_GRANTED) {
// if we have permission, then update user location. we need this check to make the code run!
if (ContextCompat.checkSelfPermission(this, Manifest.permission.ACCESS_FINE_LOCATION) == PackageManager.PERMISSION_GRANTED) {
// 0 , 0 mean always keep track of user location changes, we can change it to be every 10 seconds or something like that.
locationManager.requestLocationUpdates(LocationManager.GPS_PROVIDER, 0, 0, locationListener);
}
}
}
}