Android Develop Tricks

设置AlertDialog的大小：

		AlertDialog dialog = builder.setTitle("消息列表")
							.setView(layout)
							.create();
		dialog.show();
		//设置窗口的大小
		dialog.getWindow().setLayout(300, 200);

dialog.show();一定要放在dialog.getWindow().setLayout(300, 200);的前面，否则不起作用。

另一种实现：

WindowManager.LayoutParams params = dialog.getWindow().getAttributes();
params.width = 300;
params.height = 200;
dialog.getWindow().setAttributes(params);

实际上setLayout就是对这个方法的封装：

        final WindowManager.LayoutParams attrs = getAttributes();
        attrs.width = width;
        attrs.height = height;
        if (mCallback != null) {
            mCallback.onWindowAttributesChanged(attrs);
        }

任意位置显示View：

通过WindowManager来实现添加View：

mWindowManager = getWindowManager();
        LayoutInflater inflater = (LayoutInflater) getSystemService(LAYOUT_INFLATER_SERVICE);
        mDialogView = inflater.inflate(R.layout.dialogview, null);
        WindowManager.LayoutParams params = new WindowManager.LayoutParams();
        params.height = WindowManager.LayoutParams.WRAP_CONTENT;
        params.width = WindowManager.LayoutParams.WRAP_CONTENT;
        params.y += 100;
        params.x += -30;
        initDialogComponents(mDialogView);
        //添加对话框
        mWindowManager.addView(mDialogView, params);

任意View的触摸移动通用方法：

同样是重写onTouchEent

package ui;

import android.content.Context;
import android.util.AttributeSet;
import android.util.DisplayMetrics;
import android.util.Log;
import android.view.MotionEvent;
import android.view.WindowManager;
import android.view.animation.AlphaAnimation;
import android.view.animation.Animation;
import android.view.animation.AnimationSet;
import android.view.animation.ScaleAnimation;
import android.widget.Button;
/**
 *
 * @author chenxiruanhai
 *
 *
 */
public class MenuButton extends Button {
	private Context mContext;
	private WindowManager mWm;

	int lastX;
	int lastY;
	int screenWidth;
	int screenHeight;

	public MenuButton(Context context, AttributeSet attrs) {
		super(context, attrs);
		this.mContext = context;
		mWm = (WindowManager) mContext.getSystemService(Context.WINDOW_SERVICE);
		DisplayMetrics dm = mContext.getResources().getDisplayMetrics();
		screenWidth = dm.widthPixels;
		screenHeight = dm.heightPixels;
	}

	@Override
	public boolean onTouchEvent(MotionEvent event) {
		super.onTouchEvent(event);
		measure(0, 0);
		switch (event.getAction()) {
		case MotionEvent.ACTION_DOWN:
			lastX = (int) event.getRawX();
			lastY = (int) event.getRawY();
			break;
		case MotionEvent.ACTION_MOVE:
			int dx = (int) event.getRawX() - lastX;
			int dy = (int) event.getRawY() - lastY;
			int left = this.getLeft() + dx;
			int top = this.getTop() + dy;
			int right = this.getRight() + dx;
			int bottom = this.getBottom() + dy;
			if (left < 0) {
				left = 0;
				right = left + this.getWidth();
			}
			if (right > screenWidth) {
				right = screenWidth;
				left = right - this.getWidth();
			}
			if (top < 0) {
				top = 0;
				bottom = top + this.getHeight();
			}
			if (bottom > screenHeight) {
				bottom = screenHeight;
				top = bottom - this.getHeight();
			}
			this.layout(left, top, right, bottom);
			lastX = (int) event.getRawX();
			lastY = (int) event.getRawY();
			lastX = (int) event.getRawX();
			lastY = (int) event.getRawY();
			break;
		case MotionEvent.ACTION_UP:{
			Animation alphaAnimation = new AlphaAnimation( 0.5f,1f);
			 alphaAnimation.setDuration(1000);
			 Animation scaleAnimation2 = new ScaleAnimation(1.0f, .5f,1.0f,.5f);
			 scaleAnimation2.setDuration(500);
			 AnimationSet animationSet = new AnimationSet(true);
			 animationSet.addAnimation(alphaAnimation);
			 animationSet.addAnimation(scaleAnimation);
			 animationSet.addAnimation(scaleAnimation2);
			 animationSet.setFillAfter(true);
			Animation currentAnima = getAnimation();
			if(null!=currentAnima) {
				currentAnima.cancel();
				animationSet.reset();
			}
			 startAnimation(animationSet);
		}
			break;
		}
		return true;
	}
}

ImageView设置属性scaleType为FIT_START后去掉多余空白

	imageView.setScaleType(ImageView.FIT_START);
        imageView.setAdjustViewBounds(true);