Android studio 单击按钮删除项目
在我的Android studio 单击按钮删除项目,android-studio,sql-delete,Android Studio,Sql Delete,在我的main活动中我希望我的按钮删除我的视图列表中的所有项目。不幸的是,我在这里找到的所有解决方案都帮不了我。如果我单击“全部清除”按钮,它将删除列表中的所有项目,但这些项目仍保存在我的数据库中 我对Android Studio完全是新手,所以我不知道如何编写代码,让它按照我想要的方式工作 这是我的主要活动: package com.vorlesung.iubh.todo; import android.content.Context; import android.content.Inte
main活动中
我希望我的按钮删除我的视图列表中的所有项目。不幸的是,我在这里找到的所有解决方案都帮不了我。如果我单击“全部清除”按钮,它将删除列表中的所有项目,但这些项目仍保存在我的数据库中
我对Android Studio完全是新手,所以我不知道如何编写代码,让它按照我想要的方式工作
这是我的主要活动:
package com.vorlesung.iubh.todo;
import android.content.Context;
import android.content.Intent;
import android.database.Cursor;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.util.SparseBooleanArray;
import android.view.View;
import android.widget.ArrayAdapter;
import android.widget.Button;
import android.widget.ListView;
import android.widget.Toast;
import java.util.ArrayList;
public class MainActivity extends AppCompatActivity {
DatabaseHepler myDB;
ArrayList<String> list;
ListView myToDoList;
ArrayAdapter<String> arrayAdapter;
SparseBooleanArray selectedItem;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
Button addToDo = (Button) findViewById(R.id.addToDo);
Button clearAll = (Button) findViewById(R.id.clearALL);
Button editSelected = (Button) findViewById(R.id.editSelected);
Button clearDone = (Button) findViewById(R.id.clearDone);
myToDoList = (ListView) findViewById(R.id.myToDoList);
myDB = new DatabaseHepler(this);
list = new ArrayList<>();
Cursor data = myDB.getListContents();
if (data.getCount() == 0)
Toast.makeText(this, "The Database was empty", Toast.LENGTH_LONG).show();
else {
while (data.moveToNext()) {
list.add(data.getString(1));
arrayAdapter = new ArrayAdapter<>(this, android.R.layout.simple_list_item_multiple_choice, list);
myToDoList.setAdapter(arrayAdapter);
}
}
}
public void onClickaddToDo(View button) {
Intent newToDo = new Intent(this, AddToDo.class);
startActivity(newToDo);
}
// With this onClick I want to delete all Items from my List.
public void onClickaclearALL(View button) {
list.clear();
arrayAdapter.notifyDataSetChanged();
}
}
编辑
我的日志文件中显示了以下错误:
2018-12-23 10:16:05.627 21957-21973/com.vorlesung.iubh.todo E/eglCodecCommon: glUtilsParamSize: unknow param 0x000082da
2018-12-23 10:16:05.627 21957-21973/com.vorlesung.iubh.todo E/eglCodecCommon: glUtilsParamSize: unknow param 0x00008cdf
2018-12-23 10:16:05.628 21957-21973/com.vorlesung.iubh.todo E/eglCodecCommon: glUtilsParamSize: unknow param 0x00008824
2018-12-23 10:17:26.766 21957-21957/com.vorlesung.iubh.todo E/AndroidRuntime: FATAL EXCEPTION: main
Process: com.vorlesung.iubh.todo, PID: 21957
java.lang.IllegalStateException: Could not execute method for android:onClick
at android.support.v7.app.AppCompatViewInflater$DeclaredOnClickListener.onClick(AppCompatViewInflater.java:390)
at android.view.View.performClick(View.java:5610)
at android.view.View$PerformClick.run(View.java:22265)
at android.os.Handler.handleCallback(Handler.java:751)
at android.os.Handler.dispatchMessage(Handler.java:95)
at android.os.Looper.loop(Looper.java:154)
at android.app.ActivityThread.main(ActivityThread.java:6077)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:866)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:756)
Caused by: java.lang.reflect.InvocationTargetException
at java.lang.reflect.Method.invoke(Native Method)
at android.support.v7.app.AppCompatViewInflater$DeclaredOnClickListener.onClick(AppCompatViewInflater.java:385)
at android.view.View.performClick(View.java:5610)
at android.view.View$PerformClick.run(View.java:22265)
at android.os.Handler.handleCallback(Handler.java:751)
at android.os.Handler.dispatchMessage(Handler.java:95)
at android.os.Looper.loop(Looper.java:154)
at android.app.ActivityThread.main(ActivityThread.java:6077)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:866)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:756)
Caused by: java.lang.IllegalArgumentException: Empty bindArgs
at android.database.sqlite.SQLiteDatabase.execSQL(SQLiteDatabase.java:1656)
at com.vorlesung.iubh.todo.DatabaseHepler.deleteAllRow(DatabaseHepler.java:51)
at com.vorlesung.iubh.todo.MainActivity.onClickaclearALL(MainActivity.java:59)
at java.lang.reflect.Method.invoke(Native Method)
at android.support.v7.app.AppCompatViewInflater$DeclaredOnClickListener.onClick(AppCompatViewInflater.java:385)
at android.view.View.performClick(View.java:5610)
at android.view.View$PerformClick.run(View.java:22265)
at android.os.Handler.handleCallback(Handler.java:751)
at android.os.Handler.dispatchMessage(Handler.java:95)
at android.os.Looper.loop(Looper.java:154)
at android.app.ActivityThread.main(ActivityThread.java:6077)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:866)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:756)
private class DeleteItemsAsyncTask extends AsyncTask<Void, Void, Void> {
private Context mContext;
DeleteItemsAsyncTask(Context context) {
mContext = context;
}
@Override
protected Void doInBackground(Void... voids) {
myDB.deleteRow();
return null;
}
@Override
protected void onPostExecute(Void void) {
list.clear();
arrayAdapter.notifyDataSetChanged();
}
}
类似地,列出数据时也应该这样做。您需要在DatabaseHepler中创建一个函数,以删除表中的所有元素 在DatabasePler类中,需要编写此函数
public void deleteAllRow() {
SQLiteDatabase db = this.getWritableDatabase();
db.execSQL("delete from "+ TABLE_NAME);
db.close();
}
在您的主要活动中,需要编写以下代码:
// With this onClick I want to delete all Items from my List.
public void onClickaclearALL(View button) {
list.clear();
myDB.deleteAllRow(); // this will delete all data from the table.
arrayAdapter.notifyDataSetChanged();
}
这将对您有所帮助。您只清除了列表,但从未调用deleteRow…@Jacob是的,我知道,但我不知道我必须在哪里调用它,或者如何调用:(我必须在我的MainActivity或数据库中调用它吗?现在,如果我单击“全部清除”,应用程序将停止运行)Button2018-12-23 10:12:56.234 21718-21718/com.vorlesung.iubh.todo E/AndroidRuntime:FATAL EXCEPTION:main Process:com.vorlesung.iubh.todo,PID:21718 java.lang.IllegalStateException:无法为android执行方法:单击不确定这是否正确,但当我单击按钮时会显示此信息请更新函数delete谢谢谢谢谢谢谢谢现在它对我来说很好。非常感谢,圣诞快乐:D
public void deleteAllRow() {
SQLiteDatabase db = this.getWritableDatabase();
db.execSQL("delete from "+ TABLE_NAME);
db.close();
}
// With this onClick I want to delete all Items from my List.
public void onClickaclearALL(View button) {
list.clear();
myDB.deleteAllRow(); // this will delete all data from the table.
arrayAdapter.notifyDataSetChanged();
}