通过代码生成布局文件

通过代码生成上面的布局为：

 1 package cn.android.codeui;
 2
 3 import android.app.Activity;
 4 import android.os.Bundle;
 5 import android.view.ViewGroup.LayoutParams;
 6 import android.widget.Button;
 7 import android.widget.EditText;
 8 import android.widget.LinearLayout;
 9 import android.widget.TextView;
10 
11 public class MainActivity extends Activity {
12     /** Called when the activity is first created. */
13     @Override
14     public void onCreate(Bundle savedInstanceState) {
15         super.onCreate(savedInstanceState);
16         
17         LinearLayout linearlayout = new LinearLayout(this);
18         linearlayout.setOrientation(LinearLayout.VERTICAL);
19         
20         TextView tv = new TextView(this);
21         tv.setText("姓名");
22         LayoutParams params = new LayoutParams(LayoutParams.FILL_PARENT, LayoutParams.WRAP_CONTENT);
23         linearlayout.addView(tv, params);
24         
25         EditText et = new EditText(this);
26         linearlayout.addView(et, params);
27         
28         Button bt = new Button(this);
29         bt.setText("确定");
30         params = new LayoutParams(LayoutParams.WRAP_CONTENT, LayoutParams.WRAP_CONTENT);
31         linearlayout.addView(bt, params);
32         
33         params = new LayoutParams(LayoutParams.FILL_PARENT, LayoutParams.FILL_PARENT);
34         setContentView(linearlayout, params);
35     }
36 }

小结：一个控件只能有一个父元素，如果多次添加则会报出异常：

E/AndroidRuntime(23954):
java.lang.RuntimeException: Unable to start activity ComponentInfo{cn.android.codeui/cn.android.codeui.MainActivity}: java.lang.IllegalStateException: The specified child already has a parent. You must call removeView() on the child's parent first.