无法更改 TextView 实例的位置。答案

【问题标题】：Can't change the location of TextView's instance.无法更改 TextView 实例的位置。
【发布时间】：2012-12-26 00:26:22
【问题描述】：

public class MainActivity extends Activity implements OnGestureListener 
{ 
   private LinearLayout mainlayout;
   private TextView tv;
   private GestureDetector gestureScanner;

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

       gestureScanner = new GestureDetector(MainActivity.this,this);

       mainlayout = new LinearLayout(this);
       mainlayout.setLayoutParams(new LinearLayout.LayoutParams(LayoutParams.MATCH_PARENT,LayoutParams.MATCH_PARENT));
       mainlayout.setBackgroundColor(Color.GREEN);   


      tv = new TextView(getApplicationContext());
      tv.setBackgroundColor(Color.YELLOW);
      tv.setTextColor(Color.BLUE);
      tv.setGravity(Gravity.CENTER);   //here, why tv located top-left
      tv.setTextSize(20);
      tv.setLayoutParams(new LinearLayout.LayoutParams(320,80));
      mainlayout.addView(tv);
      setContentView(mainlayout);
  }
}

代码如上，我用xml以外的Java代码实现布局，添加一个TextView，tv。使用 tv.setGravity(Gravity.CENTER) 定位它，为什么我不能更改电视位置。我在等你的答复。先感谢您。我会感谢你的好意。

【问题讨论】：

标签： android textview location layout-gravity

【解决方案1】：

您正在使用该代码设置 TextView 内容的重心，而不是 TextView 本身的重心。尝试使用：

LinearLayout.LayoutParams lp = new LinearLayout.LayoutParams(LayoutParams.WRAP_CONTENT, LayoutParams.FILL_PARENT);
lp.gravity = Gravity.CENTER;
tv.setLayoutParams(lp);

编辑

事实证明，LinearLayout 是可行的，但只有在你改变方向并且在整个布局中只需要一个 TextView 时才有效：

private LinearLayout mainlayout;
private TextView tv;

@Override
public void onCreate(Bundle bundle) {
    super.onCreate(bundle);

    mainlayout = new LinearLayout(this);
    mainlayout.setLayoutParams(new LinearLayout.LayoutParams(LayoutParams.MATCH_PARENT, LayoutParams.MATCH_PARENT));
    mainlayout.setBackgroundColor(Color.GREEN);
    mainlayout.setOrientation(LinearLayout.VERTICAL);

    tv = new TextView(getApplicationContext());
    tv.setBackgroundColor(Color.YELLOW);
    tv.setTextColor(Color.BLUE);
    tv.setTextSize(20);
    tv.setLayoutParams(new LinearLayout.LayoutParams(320, 80));
    mainlayout.addView(tv);
    setContentView(mainlayout);

    LinearLayout.LayoutParams lp = new LinearLayout.LayoutParams(LayoutParams.WRAP_CONTENT,
            LayoutParams.WRAP_CONTENT);
    lp.gravity = Gravity.CENTER;
    tv.setLayoutParams(lp);
    tv.setText("LOL");

}

以上代码结果：

【讨论】：

如你所说，我认为 TextView 和 TextView 的内容都有 setGravity() 的方法，对吧？
你又这么亲力亲为，不胜感激

【解决方案2】：

mainlayout = new RelativeLayout(this);
        mainlayout.setLayoutParams(new LinearLayout.LayoutParams(LayoutParams.MATCH_PARENT, LayoutParams.MATCH_PARENT));
        mainlayout.setBackgroundColor(Color.GREEN);

        tv = new TextView(getApplicationContext());
        tv.setBackgroundColor(Color.YELLOW);
        tv.setTextColor(Color.BLUE);
        tv.setTextSize(20);
        tv.setGravity(Gravity.CENTER);

        tv2 = new TextView(getApplicationContext());
        tv2.setBackgroundColor(Color.YELLOW);
        tv2.setTextColor(Color.BLUE);
        tv2.setTextSize(20);
        tv2.setGravity(Gravity.CENTER);

        RelativeLayout.LayoutParams params= new RelativeLayout.LayoutParams(320, 80);
        params.addRule(RelativeLayout.CENTER_IN_PARENT);

        tv.setLayoutParams(params);

        RelativeLayout.LayoutParams params2= new RelativeLayout.LayoutParams(320, 80);
        tv2.setLayoutParams(params2);


        mainlayout.addView(tv);
        mainlayout.addView(tv2);

        setContentView(mainlayout);

【讨论】：

这会影响布局中所有元素的重力。 OP 只想影响 TextView