Android--动态添加控件

package com.mrzhu.edittest;

import android.app.Activity;
import android.os.Bundle;
import android.view.ViewGroup;
import android.widget.RelativeLayout;

public class EditTestActivity extends Activity {
	/** Called when the activity is first created. */
	@Override
	public void onCreate(Bundle savedInstanceState) {
		super.onCreate(savedInstanceState);
		//自定义的带提示文本的EditText组件
		EditTextTest ed = new EditTextTest(this);
		//设置从左边140px处开始输入文本
		ed.setPadding(140, 0, 0, 0);
		//装载一个布局文件，向这个布局中动态添加一个EditText
		RelativeLayout relativeLayout = (RelativeLayout) getLayoutInflater().inflate(R.layout.main, null);
		//创建一个LayoutParams对象
		RelativeLayout.LayoutParams layoutParams = new RelativeLayout.LayoutParams(ViewGroup.LayoutParams.FILL_PARENT, ViewGroup.LayoutParams.WRAP_CONTENT);
		//设置android:layout_below属性的值 
		layoutParams.addRule(RelativeLayout.BELOW, R.id.button2);
		//动态添加EditText
		relativeLayout.addView(ed, layoutParams);
		//设置布局
		setContentView(relativeLayout);
	}
}

自定义的EditText控件：

package com.mrzhu.edittest;

import android.content.Context;
import android.graphics.Canvas;
import android.graphics.Color;
import android.graphics.Paint;
import android.util.AttributeSet;
import android.widget.EditText;

public class EditTextTest extends EditText {

	public EditTextTest(Context context) {
		super(context);
	}
	
	public EditTextTest(Context context, AttributeSet attrs, int defStyle) {
		super(context, attrs, defStyle);
	}

	public EditTextTest(Context context, AttributeSet attrs) {
		super(context, attrs);
	}

	@Override
	protected void onDraw(Canvas canvas) {
		Paint paint = new Paint();
		paint.setTextSize(20);
		paint.setColor(Color.GRAY);
		canvas.drawText("输入提示文本:", 10, getHeight() / 2 + 5, paint);
		super.onDraw(canvas);
	}
}

main.xml:

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:id="@+id/linearlayout"
    android:layout_width="fill_parent"
    android:layout_height="fill_parent"
    android:orientation="horizontal" >

    <Button
        android:id="@+id/button2"
        android:layout_width="80dp"
        android:layout_height="80dp"
        android:layout_alignParentTop="true"
        android:layout_centerHorizontal="true"
        android:layout_marginTop="150dp"
        android:onClick="click"
        android:text="Button" />

</RelativeLayout>