在android中以編程方式創建和添加TextView

Question

我正在嘗試將TextView添加到may RelativeLayout中。它不工作。

public class MainActivity extends Activity { 

    @Override 
    protected void onCreate(Bundle savedInstanceState) { 
     super.onCreate(savedInstanceState); 

     RelativeLayout rl = (RelativeLayout) findViewById(R.layout.activity_main); 
     TextView tv = new TextView(MainActivity.this); 

     tv.setText("Hello World"); 
     tv.setTextColor(Color.BLACK); 
     tv.setLayoutParams(new LayoutParams(LayoutParams.MATCH_PARENT,LayoutParams.WRAP_CONTENT)); 
     rl.addView(tv);  
     setContentView(R.layout.activity_main); 

    } 

Answer 1

您應該在super.onCreate之後立即致電setContentView(R.layout.activity_main)。

我這樣做：

1. 我去main_activity.xml和添加的屬性android:id="@+id/activity_main"到RelativeLayout的。

2. 編輯的代碼：

   @Override 
   protected void onCreate(Bundle savedInstanceState) { 
       super.onCreate(savedInstanceState); 
       setContentView(R.layout.activity_main); 
   
       //RelativeLayout rl = (RelativeLayout) findViewById(R.layout.activity_main); 
       RelativeLayout rl = (RelativeLayout) findViewById(R.id.activity_main); 
       TextView tv = new TextView(MainActivity.this); 
   
       tv.setText("Hello World"); 
       tv.setTextColor(Color.BLACK); 
       tv.setLayoutParams(new LayoutParams(LayoutParams.MATCH_PARENT,LayoutParams.WRAP_CONTENT)); 
       rl.addView(tv);  
   
   } 
   

   但儘管如此，TextView的重疊將在RelativeView等產生的物品。也許你應該考慮使用LinearLayout而不是垂直方向。

Answer 2

致電setContentView(R.layout.activity_main)將重新佈局您的佈局，覆蓋您之前添加的佈局。將它上移，所以這是撥打super後的第一件事。例如：

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

    RelativeLayout rl = (RelativeLayout) findViewById(R.layout.activity_main); 
    TextView tv = new TextView(MainActivity.this); 

    tv.setText("Hello World"); 
    tv.setTextColor(Color.BLACK); 
    tv.setLayoutParams(new LayoutParams(LayoutParams.MATCH_PARENT,LayoutParams.WRAP_CONTENT)); 
    rl.addView(tv);  
}