Question

在我的基于android数据库的应用程序中。当我从数据库中检索数据时，它一次又一次获得相同的值（第一个值插入数据库）。有什么问题？

插入数据类

public class MainActivity extends AppCompatActivity {
public String dataBase_Name="database";
public static DatabaseHelper database;
private TextView text;
private GestureDetector gestureDetector;
private  View.OnTouchListener gestureListener;

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);
    final DatabaseHelper database1=new DatabaseHelper(this,dataBase_Name);
    database=database1;
    Button add=(Button)findViewById(R.id.button);
    text=(TextView)findViewById(R.id.editText);
    add.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View v) {
            String temp=text.getText().toString();
            database.insert(temp);
            text.setText("");
        }
    });
    Button next=(Button) findViewById(R.id.button6);
    Button prev=(Button) findViewById(R.id.button4);
    next.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View v) {
            Intent intent = new Intent(MainActivity.this, Delete.class);
            MainActivity.this.startActivity(intent);

        }
    });
    prev.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View v) {
            Intent intent = new Intent(MainActivity.this, com.example.partha.app4.View.class);
            MainActivity.this.startActivity(intent);
        }
    });


}

}

检索课程

public class View extends  MainActivity {
private GestureDetector gestureDetector;
private  android.view.View.OnTouchListener gestureListener;
ArrayAdapter<String> adapter;
 ListView listView;
@Override
protected void onCreate(Bundle savedInstanceState) {
    try {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_view);
        listView = (ListView) findViewById(R.id.listView);
        String[] load = database.get_all_entry();
        String[] temp=database.get_all_entry();
        Toast.makeText(this,"Length "+temp.length,Toast.LENGTH_LONG);
        for(int i=0;i<temp.length;i++)
        {
            Toast.makeText(this,temp[i],Toast.LENGTH_SHORT);
        }
        if (load != null) {
            adapter = new ArrayAdapter<String>(this, R.layout.item,R.id.textView, database.get_all_entry());
            listView.setAdapter(adapter);
        } else {
            Toast.makeText(this, "Data cant found", Toast.LENGTH_SHORT);
        }
        Button next = (Button) findViewById(R.id.button11);
        Button prev = (Button) findViewById(R.id.button10);
        next.setOnClickListener(new android.view.View.OnClickListener() {
            @Override
            public void onClick(android.view.View v) {
                clear();
                Intent intent = new Intent(View.this, MainActivity.class);
                View.this.startActivity(intent);

            }
        });
        prev.setOnClickListener(new android.view.View.OnClickListener() {
            @Override
            public void onClick(android.view.View v) {
                clear();
                Intent intent = new Intent(View.this, Update.class);
                View.this.startActivity(intent);

            }
        });

    } catch (Exception e) {
        Log.e("view", e.toString());
    }
}
void clear()
{
    listView.setAdapter(null);
}

}

Databasehelper Class

public class DatabaseHelper extends SQLiteOpenHelper {
public static String databaseName;
public static final String CONTACTS_TABLE_NAME = "contacts";
public static final String CONTACTS_COLUMN_ID = "id";
public static final String CONTACTS_COLUMN_NAME = "name";
Context context1;

DatabaseHelper(Context context,String databaseName)
{
    super(context,databaseName,null,1);
    this.databaseName=databaseName;
    context1=context;


}
@Override
public void onCreate(SQLiteDatabase db) {
    db.execSQL("create table contacts" + "(" + CONTACTS_COLUMN_ID + " integer primary key,name text)");

}

@Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
    db.execSQL("DROP TABLE IF EXISTS contacts");
    onCreate(db);

}
public boolean insert(String name)
{
    SQLiteDatabase db=this.getWritableDatabase();
    ContentValues contentValues=new ContentValues();
    contentValues.put("name", name);
    db.insert("contacts", null, contentValues);
    return true;

}
public Cursor getData(int id){
    SQLiteDatabase db = this.getReadableDatabase();
    Cursor res =  db.rawQuery( "select * from contacts where id="+id+"", null );
    return res;
}
public boolean update (Integer id, String name)
{
    SQLiteDatabase db = this.getWritableDatabase();
    ContentValues contentValues = new ContentValues();
    contentValues.put("name", name);
    db.update("contacts", contentValues, "id = ? ", new String[]{Integer.toString(id)});
    return true;
}
public  int find(String name)
{
    SQLiteDatabase db=this.getReadableDatabase();
    Cursor cursor=db.query("contacts", new String[]{"name"}, "name = ?", new String[]{name}, null, null, null);
    cursor.moveToFirst();
    if((cursor!=null)&&(cursor.getCount()!=0)) {
        int id = cursor.getInt(cursor.getColumnIndex(CONTACTS_COLUMN_ID));
        return id;
    }
    else
    {
        return -1;
    }

}
public Integer delete (Integer id)
{
    SQLiteDatabase db = this.getWritableDatabase();
    return db.delete("contacts",
            "id = ? ",
            new String[] { Integer.toString(id) });
}
public String[] get_all_entry()
{
    SQLiteDatabase db=this.getReadableDatabase();
    Cursor cursor=db.query("contacts",null,null,null,null,null,null);


    cursor.moveToFirst();
    if((cursor!=null)&&(cursor.getCount()!=0))
    {
        String []name=new String[cursor.getCount()];

        for(int i=0;i<cursor.getCount();i++)
        {
            name[i]=(cursor.getString(cursor.getColumnIndex(CONTACTS_COLUMN_NAME)));
        }

        return name;
    }
    else
    {
        return null;
    }

}
}

Answer 1

您在cursor.moveToNext();的循环中遗漏了get_all_entry() 所以你在调用cursor.moveToFirst();

后用相同的光标记录（第一条记录）填充数组项

修改你的for循环如下：

for(int i=0;i<cursor.getCount();i++){
    name[i]=(cursor.getString(cursor.getColumnIndex(CONTACTS_COLUMN_NAME)));
    cursor.moveToNext(); // <---- ADD THIS
}

P.S：考虑使用while(cursor.moveToNext()){}来读取光标记录，我认为这比使用for loop更好

Android数据库一次又一次显示相同的值

1 个答案: