我正在尝试在 Sqlite 数据库 中添加当前位置的纬度和经度。
但是当我打开我的 Activity 时，它会崩溃并显示 android.database.sqlite.SQLiteOpenHelper.getDatabaseLocked(SQLiteOpenHelper.java:252)
我不明白有什么问题。
我的代码是
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main_page);
try {
setUpMapIfNeeded();
}catch (Exception e){
e.printStackTrace();
Toast.makeText(MainPage.this, "Google Play Services Out of Date. Please Update.", Toast.LENGTH_SHORT).show();
}
googleMap.setMyLocationEnabled(true);
googleMap.getUiSettings().setMyLocationButtonEnabled(true);
googleMap.getUiSettings().setMapToolbarEnabled(false);
googleMap.getUiSettings().setZoomControlsEnabled(true);
locMan =(LocationManager)getSystemService(Context.LOCATION_SERVICE);
locMan.requestLocationUpdates(LocationManager.GPS_PROVIDER,0,0,this);
Button btnRecord=(Button)findViewById(R.id.button);
btnRecord.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
LocationManager locationManager=(LocationManager)getSystemService(Context.LOCATION_SERVICE);
locationManager.requestLocationUpdates(LocationManager.GPS_PROVIDER, 0, 0, new LocationListener() {
@Override
public void onLocationChanged(Location location) {
LatLng latLng=new LatLng(location.getLatitude(),location.getLongitude());
double latitude=location.getLatitude();
double longitude=location.getLongitude();
ContentValues cv=new ContentValues();
try{
DatabaseHelper databaseHelper=new DatabaseHelper(MainPage.this);
SQLiteDatabase db=databaseHelper.getReadableDatabase();
cv.put("latitude",latitude);
cv.put("longitude",longitude);
long insert=db.insert("latLngTable",null,cv);
if (insert!=-1){
Toast.makeText(MainPage.this,"Datas Inserted",Toast.LENGTH_SHORT).show();
}else {
Toast.makeText(MainPage.this,"Insertion Failed",Toast.LENGTH_SHORT).show();
}
}catch (SQLiteException e){
Toast.makeText(MainPage.this,e.getMessage(),Toast.LENGTH_SHORT).show();
}
}
@Override
public void onStatusChanged(String provider, int status, Bundle extras) {
}
@Override
public void onProviderEnabled(String provider) {
}
@Override
public void onProviderDisabled(String provider) {
}
});
}
});
}
@Override
public boolean onCreateOptionsMenu(Menu menu) {
getMenuInflater().inflate(R.menu.menu_main_page, menu);
return true;
}
@Override
public boolean onOptionsItemSelected(MenuItem item) {
int id = item.getItemId();
if (id == R.id.viewLocations) {
Intent i=new Intent(MainPage.this,LocationsList.class);
startActivity(i);
return true;
}
return super.onOptionsItemSelected(item);
}
@Override
protected void onResume() {
super.onResume();
setUpMapIfNeeded();
}
private void setUpMapIfNeeded() {
if (googleMap == null) {
googleMap = ((MapFragment) getFragmentManager().findFragmentById(R.id.map))
.getMap();
if (googleMap != null) {
setUpMap();
}
}
}
private void setUpMap() {
//googleMap.addMarker(new MarkerOptions().position(new LatLng(latitude, longitude)).icon(bitmapDescriptor).title(locality).snippet(""));
}
@Override
public void onLocationChanged(Location location) {
LatLng latLng1 = new LatLng(location.getLatitude(), location.getLongitude());
CameraUpdate cameraUpdate = CameraUpdateFactory.newLatLngZoom(latLng1, 16.5f);
googleMap.animateCamera(cameraUpdate);
locMan.removeUpdates(this);
}
@Override
public void onStatusChanged(String provider, int status, Bundle extras) {
}
@Override
public void onProviderEnabled(String provider) {
}
@Override
public void onProviderDisabled(String provider) {
}
我使用SQLiteOpenHelper来创建我的数据库。
我以前使用它们没有错误，但现在我收到此错误。
请大家帮忙。
我的SQLiteOpenHelper是
public class DatabaseHelper extends SQLiteOpenHelper {
public static final String db_name="latLngDB";
public static final int version=1;
Context context;
public DatabaseHelper(Context context){
super(context,db_name,null,version);
}
@Override
public void onCreate(SQLiteDatabase db){
db.execSQL("create table latLngTable(_id INTEGER PRIMARY KEY AUTOINCREMENT,latitude integer,longitude integer)");
Toast.makeText(context,"Database Created",Toast.LENGTH_SHORT).show();
}
@Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion){
if (oldVersion>=newVersion)
return;
if (oldVersion==1){
Log.d("New Version","Data's can be Upgraded");
}
Log.d("Sample Data", "onUpgrade:" + newVersion);
}
}
LogCat is
07-22 15:31:17.652 14125-14125/? E/AndroidRuntime﹕ FATAL EXCEPTION: main
Process: com.realtech.latlngrecorder, PID: 14125
java.lang.NullPointerException
at android.widget.Toast.<init>(Toast.java:93)
at android.widget.Toast.makeText(Toast.java:241)
at com.realtech.latlngrecorder.DatabaseHelper.onCreate(DatabaseHelper.java:22)
at android.database.sqlite.SQLiteOpenHelper.getDatabaseLocked(SQLiteOpenHelper.java:252)
at android.database.sqlite.SQLiteOpenHelper.getReadableDatabase(SQLiteOpenHelper.java:188)
at com.realtech.latlngrecorder.MainPage$1$1.onLocationChanged(MainPage.java:67)
at android.location.LocationManager$ListenerTransport._handleMessage(LocationManager.java:279)
at android.location.LocationManager$ListenerTransport.access$000(LocationManager.java:208)
at android.location.LocationManager$ListenerTransport$1.handleMessage(LocationManager.java:224)
at android.os.Handler.dispatchMessage(Handler.java:110)
at android.os.Looper.loop(Looper.java:193)
at android.app.ActivityThread.main(ActivityThread.java:5292)
at java.lang.reflect.Method.invokeNative(Native Method)
at java.lang.reflect.Method.invoke(Method.java:515)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:824)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:640)
at dalvik.system.NativeStart.main(Native Method)
最佳答案
您没有将有效的Context传递给SQLiteOpenHelper构造函数。这就是 getDatabaseLocked() 中 NPE 的解释。
您发布的堆栈跟踪显示您有 NPE 在帮助器 onCreate() 中初始化 Toast。请注意，您的成员变量 context 尚未初始化。
关于java - android.database.sqlite.SQLiteOpenHelper.getDatabaseLocked(SQLiteOpenHelper.java :252) nullpointerexception，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/31559542/