我怎样才能让我的按钮在左下角？

Question

我想让按钮到左下方。为什么这不工作？我尝试了2个小时，但无法实现。 :(

RelativeLayout rl = new RelativeLayout(this); 
    RelativeLayout.LayoutParams firstImageParams = new RelativeLayout.LayoutParams(
      android.view.ViewGroup.LayoutParams.MATCH_PARENT, 
      android.view.ViewGroup.LayoutParams.MATCH_PARENT); 
    Button b = new Button(this); 
    b.setText("take photo"); 
    b.setGravity(Gravity.BOTTOM | Gravity.LEFT); 
    b.setOnClickListener(new View.OnClickListener() { 
     public void onClick(View v) { 
      Toast.makeText(getApplicationContext(), "Select Area of Interest", Toast.LENGTH_SHORT).show(); 
     } 
    }); 
    rl.addView(mGrabView,firstImageParams); 
    rl.addView(b); 
    rl.setGravity(Gravity.CENTER_HORIZONTAL | Gravity.CENTER_VERTICAL); 
    this.addContentView(rl,new LayoutParams(LayoutParams.MATCH_PARENT, LayoutParams.MATCH_PARENT)); 

Answer 1

你你为什么不使用XML布局反正需要布局参数添加到该按钮，而不是重力。

RelativeLayout rl = new RelativeLayout(this); 

Button b = new Button(this); 
b.setText("take photo"); 
b.setOnClickListener(new View.OnClickListener() { 
    public void onClick(View v) { 
     Toast.makeText(getApplicationContext(), "Select Area of Interest", Toast.LENGTH_SHORT).show(); 
    } 
}); 

RelativeLayout.LayoutParams lp = new RelativeLayout.LayoutParams(
    RelativeLayout.LayoutParams.WRAP_CONTENT, RelativeLayout.LayoutParams.FILL_PARENT); 
lp.addRule(RelativeLayout.ALIGN_PARENT_BOTTOM, true); 
lp.addRule(RelativeLayout.ALIGN_PARENT_LEFT, true); 
rl.addView(b, lp); 

Answer 2

？他们一般更容易理解并作出。