Question

我有2个活动，当我在第一个活动中输入内容并按＆＃34;保存按钮＆＃34;它通过SQLite数据库保存文本。在第二个活动中，我有一个已保存项目的列表，当我单击其中一个时，onItemClick方法需要触发并打开第三个活动，我可以在其中编辑或删除所选项目。现在，当我点击一个项目时，一切正常。当我点击它时，第三个活动加载，但没有显示任何内容，几秒钟后它关闭并让我回到之前的活动。这是代码片段：

第二项活动的代码段，其中列表为：

  DatabaseHelper mDatabaseHelper;
private ListView mListView;
@Override
protected  void onCreate(@Nullable Bundle savedInstanceState){
    super.onCreate(savedInstanceState);
    setContentView(R.layout.list_layout);
    mListView=(ListView) findViewById(R.id.listView);
    mDatabaseHelper=new DatabaseHelper(this);
    populateListView();
}
private void populateListView() {
    Log.d(TAG,"populateListView: Displaying data in ListView.");
    Cursor data=mDatabaseHelper.getData();
    ArrayList<String> listData=new ArrayList<>();
    while (data.moveToNext()){
        listData.add(data.getString(1));
    }
    ListAdapter adapter = new ArrayAdapter<>(this,android.R.layout.simple_list_item_1, listData);
    mListView.setAdapter(adapter);
    mListView.setOnItemClickListener(new AdapterView.OnItemClickListener() {
        @Override
        public void onItemClick(AdapterView<?> adapterView, View view, int i, long l) {
            //string name=the item saved
            String name = adapterView.getItemAtPosition(i).toString();
            Log.d(TAG,"onItemClick: You Clicked on "+ name);
            Cursor data=mDatabaseHelper.getItemID(name);
            int itemID= -1;
            while (data.moveToNext()){
                itemID = data.getInt(0);
            }
            if (itemID > -1){
                Log.d(TAG,"onItemClick: The ID is: "+itemID);
                Intent editScreenIntent = new Intent(MoneyTracking.this, EditDataActivity.class);
                editScreenIntent.putExtra("id",itemID);
                editScreenIntent.putExtra("name",name);
                startActivity(editScreenIntent);
            }
            else{
                toastMessage("No ID associated with that list item.");
            }
        }
    });
}
/**
 * Customizable toast
 * @param message
 */
private void toastMessage(String message){
    Toast.makeText(this,message,Toast.LENGTH_SHORT).show();
}}

然后＆＃34;第三个活动＆＃34;它不会加载：

private Button btnSave2, btnDelete1;
private EditText editText00;
DatabaseHelper mDatabaseHelper;
private String selectedName;
private int selectedID;

@Override
protected void  onCreate(@Nullable Bundle savedInstanceState){
    super.onCreate(savedInstanceState);
    setContentView(R.layout.edit_data_layout);
    btnSave2=(Button)findViewById(R.id.btnSaveTwo);
    btnDelete1=(Button)findViewById(R.id.btnDelete);
    editText00=(EditText) findViewById(R.id.editText00);
    mDatabaseHelper=new DatabaseHelper(this);

    Intent recievedIntent=getIntent();
    selectedID=recievedIntent.getIntExtra("id",-1);
    selectedName=recievedIntent.getStringExtra("name");
    editText00.setText(selectedName);

    btnSave2.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View v) {
            String item=editText00.getText().toString();
            if (!item.equals("")){
                mDatabaseHelper.updateName(item,selectedID,selectedName);
            }else{
                toastMessage("Morate uneti nesto da bi ste sacuvali!");
            }
        }
    });
    btnDelete1.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View v) {
            mDatabaseHelper.deleteName(selectedID,selectedName);
            editText00.setText("");
            toastMessage("Izbrisano!");
        }
    });
}
/**
 * Customizable toast
 * @param message
 */
private void toastMessage(String message){
    Toast.makeText(this,message,Toast.LENGTH_SHORT).show();
}

}

数据库助手：

private  static final String TAG="DatabaseHelper";

private  static  final String TABLE_NAME="mt_lists";
private  static  final String COL1= "ID";
private  static  final String COL2= "listndprice";


public DatabaseHelper(Context context) {
    super(context, TABLE_NAME, null, 1);
}

@Override
public void onCreate(SQLiteDatabase db) {
    String createTable="CREATE TABLE "+ TABLE_NAME +" (ID INTEGER PRIMARY KEY AUTOINCREMENT, "+
            COL2+" TEXT)";
    db.execSQL(createTable);
}
@Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
    db.execSQL("DROP TABLE IF EXISTS "+TABLE_NAME);
    onCreate(db);
}
public  boolean appData(String item)
{
    SQLiteDatabase db=this.getWritableDatabase();
    ContentValues contentValues = new ContentValues();
    contentValues.put(COL2, item);

    Log.d(TAG, "appData: Adding "+item+" to "+TABLE_NAME);
    long result=db.insert(TABLE_NAME, null, contentValues);

    if (result == -1){
        return false;
    }
    else {
        return true;
    }
}

/**
 * Returns all the data from database
 * @return
 */
public Cursor getData(){
    SQLiteDatabase db = this.getWritableDatabase();
    String query="SELECT * FROM " + TABLE_NAME;
    Cursor data=db.rawQuery(query,null);
    return  data;
}

/**
 *
 * @param name
 * @return
 */
public Cursor getItemID(String name){
    SQLiteDatabase db = this.getWritableDatabase();
    String query="SELECT"+ COL1 +" FROM "+TABLE_NAME+" WHERE "+COL2+ " = '" + name + " ' ";
    Cursor data = db.rawQuery(query,null);
    return data;
}

/**
 * Update database
 * @param newName
 * @param id
 * @param oldName
 */
public void updateName(String newName,int id,String oldName){
    SQLiteDatabase db=this.getWritableDatabase();
    String query="UPDATE"+TABLE_NAME+"SET"+COL2+"='"+newName+"' WHERE"+COL1+"= '"+id+"'"+"AND"+COL2+"= '"+oldName+"'";
    Log.d(TAG,"updateName: query: "+query);
    Log.d(TAG,"updateName: Setting name to  "+newName);
    db.execSQL(query);
}
/**
 * Delete from database
 * @param id
 * @param name
 */
public void deleteName(int id,String name){
    SQLiteDatabase db=this.getWritableDatabase();
    String query="DELETE FROM" + TABLE_NAME + "WHERE" + COL1 + "= '" + id + "'" + " AND " + COL2 + "= '" +name +"'";
    Log.d(TAG,"deleteName: query: "+query);
    Log.d(TAG,"deleteName: Deleting "+name+"from database.");
    db.execSQL(query);
}

EDIT logcat的： enter image description here

Answer 1

好的我觉得我发现了你的问题。您需要在SQL关键字和列名/值之间放置一个空格。在您的代码中，您的查询被写为“SELECTID FROM ...”。但它需要阅读“SELECT ID FROM ...”。注意SELECT和ID之间的空格！：

    public Cursor getItemID(String name){
    SQLiteDatabase db = this.getWritableDatabase();
    String query="SELECT"+ COL1 +" FROM "+TABLE_NAME+" WHERE "+COL2+ " = '" + name + " ' ";
    Cursor data = db.rawQuery(query,null);
    return data;
}

将上述内容更改为

public Cursor getItemID(String name){
    SQLiteDatabase db = this.getWritableDatabase();
    String query="SELECT "+ COL1 +" FROM "+TABLE_NAME+" WHERE "+COL2+ " = '" + name + " ' ";
    Cursor data = db.rawQuery(query,null);
    return data;
}

还要确保您的其他SQL方法没有同样的问题！

onItemClick加载空活动

1 个答案: