寫數據到數據庫

我試圖用這個代碼寫的東西到DB：（從here了和編輯一點點）寫數據到數據庫

package com.example.db; 
    import android.app.Activity; 
    import android.database.Cursor; 
    import android.database.sqlite.SQLiteDatabase; 
    import android.os.Bundle; 
    import android.util.Log; 
    import android.view.View; 
    import android.widget.EditText; 
    import android.widget.TextView; 
    public class MainActivity extends Activity { 
    String entered; 

    public void onClick (View v){ 
     EditText et = (EditText)findViewById(R.id.et); 
      entered = et.getText().toString(); 
    } 
    @Override 
    public void onCreate(Bundle savedInstanceState) { 
     super.onCreate(savedInstanceState); 
    EditText et = (EditText)findViewById(R.id.et); 
     entered = et.getText().toString(); 
     SQLiteDatabase myDB= null; 
     String TableName = "myTable"; 

     String Data=""; 


     try { 
     myDB = this.openOrCreateDatabase("DatabaseName", MODE_PRIVATE, null); 


     myDB.execSQL("CREATE TABLE IF NOT EXISTS " 
     + TableName 
     + " (Field1 STRING, Field2 INT(3));"); 


     myDB.execSQL("INSERT INTO " 
     + TableName 
     + " (Field1, Field2)" 
     + " VALUES ("+entered+", 22);"); 


     Cursor c = myDB.rawQuery("SELECT * FROM " + TableName , null); 

     int Column1 = c.getColumnIndex("Field1"); 
     int Column2 = c.getColumnIndex("Field2"); 


     c.moveToFirst(); 
     if (c != null) { 

     do { 
     String Name = c.getString(Column1); 
     int Age = c.getInt(Column2); 
     Data =Data +Name+"/"+Age+"\n"; 
     }while(c.moveToNext()); 
     } 
     TextView tv = (TextView)findViewById(R.id.tv); 
     tv.setText(Data); 

     } 
     catch(Exception e) { 
     Log.e("Error", "Error", e); 
     } finally { 
     if (myDB != null) 
     myDB.close(); 
     } 
    } 

    }

但它不工作。當我開始時，關閉程序。哪裏是不正常的東西？我該怎麼做？

來源

2014-06-25 Roki20121

Logcat，請。 http://stackoverflow.com/questions/23353173/unfortunately-myapp-has-stopped-how-can-i-solve-this – laalto

看來你忘了添加setContentView(R.layout.activity_main);，因爲在OnCreateedittext et是null。

所以添加爲

@Override 
    public void onCreate(Bundle savedInstanceState) { 
     super.onCreate(savedInstanceState); 
     setContentView(R.layout.activity_main);

變化activity_main與你的XML佈局文件。

來源

2014-06-25 16:43:37

寫數據到數據庫

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