通过代码生成布局文件

通过代码生成上面的布局为：

package cn.android.codeui;

import android.app.Activity;
import android.os.Bundle;
import android.view.ViewGroup.LayoutParams;
import android.widget.Button;
import android.widget.EditText;
import android.widget.LinearLayout;
import android.widget.TextView;

public class MainActivity extends Activity {
    /** Called when the activity is first created. */
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        
        LinearLayout linearlayout = new LinearLayout(this);
        linearlayout.setOrientation(LinearLayout.VERTICAL);
        
        TextView tv = new TextView(this);
        tv.setText("姓名");
        LayoutParams params = new LayoutParams(LayoutParams.FILL_PARENT, LayoutParams.WRAP_CONTENT);
        linearlayout.addView(tv, params);
        
        EditText et = new EditText(this);
        linearlayout.addView(et, params);
        
        Button bt = new Button(this);
        bt.setText("确定");
        params = new LayoutParams(LayoutParams.WRAP_CONTENT, LayoutParams.WRAP_CONTENT);
        linearlayout.addView(bt, params);
        
        params = new LayoutParams(LayoutParams.FILL_PARENT, LayoutParams.FILL_PARENT);
        setContentView(linearlayout, params);
    }
}

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.