public class Util extends Application {
public void deleteall(){
243 SQLiteDBUtil db2 = new SQLiteDBUtil(getApplicationContext());
SQLiteDatabase sd2 = db2
.getWritableDatabase();
String sql = "delete from user";
String sql2 = "delete from kebiao";
String sql3 = "delete from note";
sd2.execSQL(sql);
sd2.execSQL(sql2);
sd2.execSQL(sql3);
// 這里進行關閉
db2.close();
}
}
public class MainActivity extends FragmentActivity implements OnClickListener {
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
requestWindowFeature(Window.FEATURE_NO_TITLE);
setContentView(R.layout.activity_main);
Util util = new Util();
util.deleteall();
}
}
E/AndroidRuntime: FATAL EXCEPTION: main
Process: com.example.easytablemore, PID: 8427
java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.easytablemore/com.example.easytablemore.MainActivity}: java.lang.NullPointerException: Attempt to invoke virtual method 'android.content.Context android.app.Activity.getApplicationContext()' on a null object reference
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:3270)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:3409)
at android.app.servertransaction.LaunchActivityItem.execute(LaunchActivityItem.java:83)
at android.app.servertransaction.TransactionExecutor.executeCallbacks(TransactionExecutor.java:135)
at android.app.servertransaction.TransactionExecutor.execute(TransactionExecutor.java:95)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:2016)
at android.os.Handler.dispatchMessage(Handler.java:107)
at android.os.Looper.loop(Looper.java:214)
at android.app.ActivityThread.main(ActivityThread.java:7356)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:492)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:930)
Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'android.content.Context android.app.Activity.getApplicationContext()' on a null object reference
at Util.Util.deleteall(Util.java:243)
at com.example.easytablemore.MainActivity.onCreate(MainActivity.java:84)
at android.app.Activity.performCreate(Activity.java:7802)
at android.app.Activity.performCreate(Activity.java:7791)
at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1299)
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:3245)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:3409)
at android.app.servertransaction.LaunchActivityItem.execute(LaunchActivityItem.java:83)
at android.app.servertransaction.TransactionExecutor.executeCallbacks(TransactionExecutor.java:135)
at android.app.servertransaction.TransactionExecutor.execute(TransactionExecutor.java:95)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:2016)
at android.os.Handler.dispatchMessage(Handler.java:107)
at android.os.Looper.loop(Looper.java:214)
at android.app.ActivityThread.main(ActivityThread.java:7356)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:492)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:930)
Process 8427 terminated.
uj5u.com熱心網友回復：
報的空指標,在MainActivity84行,背景關系為空uj5u.com熱心網友回復：
很奇怪，我在oncreate里面直接執行deleteall里面這段代碼不會報這個錯，在oncreate里面呼叫deleteall這個方法就會報錯uj5u.com熱心網友回復：
你這個util是一個application ，你直接在util的oncreate中執行這個deleteall方法不就行了uj5u.com熱心網友回復：
哪有new application的？哪有utils繼承application的？
加個入參傳一個context就行了，并且把extends application刪掉
uj5u.com熱心網友回復：
好，我有時間試試上面諸位的方法uj5u.com熱心網友回復：
上面諸位，感謝了uj5u.com熱心網友回復：
public class Util {public void deleteall(Context context){
SQLiteDBUtil db2 = new SQLiteDBUtil(context));
SQLiteDatabase sd2 = db2
.getWritableDatabase();
String sql = "delete from user";
String sql2 = "delete from kebiao";
String sql3 = "delete from note";
sd2.execSQL(sql);
sd2.execSQL(sql2);
sd2.execSQL(sql3);
// 這里進行關閉
db2.close();
}
}
在你的Activity中呼叫的時候Util. deleteall(this);
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標籤：Android
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