Go语言视频零基础入门到精通

apekji

    如何实现androd主页面的左右拖动效果。实现起来很简单，就是使用ViewFlipper来将您要来回拖动的View装在一起，然后与GestureDetector手势识别类来联动，确定要显示哪个View，加上一点点动画效果即可。比如当手指向左快速滑动时跳转到上一个View，手指向右快速滑动时跳转到下一个View，本例中使用图片作为各个View的页面，实现左右快速滑动显示不同的图片。

       如上所示，在ViewFlipper中放置多个layout（接下来会在不同的layout中来回滑动），ViewFlipper在同一个页面就显示其中一个layout。ViewFlipper中的四个layout很简单，我们就放置一张图片，如下所示：

　　接下来我们来看看Activity，我们的Activity需要实现两个接口OnGestureListener,OnTouchListener。具体的代码如下所示，代码中都有相应的注释，这里就不再详述。

java代码： package eoe.demo;





import android.app.Activity;

import android.os.Bundle;

import android.view.GestureDetector;

import android.view.MotionEvent;

import android.view.View;

import android.view.GestureDetector.OnGestureListener;

import android.view.View.OnTouchListener;

import android.view.animation.AccelerateInterpolator;

import android.view.animation.Animation;

import android.view.animation.TranslateAnimation;

import android.widget.ViewFlipper;





public class ViewFlipperDemo extends Activity implements OnGestureListener,OnTouchListener{

private ViewFlipper mFlipper;

GestureDetector mGestureDetector;

private int mCurrentLayoutState;

private static final int FLING_MIN_DISTANCE = 100;

private static final int FLING_MIN_VELOCITY = 200;



@Override

public void onCreate(Bundle savedInstanceState) {

super.onCreate(savedInstanceState);

setContentView(R.layout.main);

mFlipper = (ViewFlipper) findViewById(R.id.flipper);

//注册一个用于手势识别的类

mGestureDetector = new GestureDetector(this);

//给mFlipper设置一个listener

mFlipper.setOnTouchListener(this);

mCurrentLayoutState = 0;

//允许长按住ViewFlipper,这样才能识别拖动等手势

mFlipper.setLongClickable(true);

}



/**

* 此方法在本例中未用到，可以指定跳转到某个页面

* @param switchTo

*/

public void switchLayoutStateTo(int switchTo) {

while (mCurrentLayoutState != switchTo) {

if (mCurrentLayoutState > switchTo) {

mCurrentLayoutState–;

mFlipper.setInAnimation(inFromLeftAnimation());

mFlipper.setOutAnimation(outToRightAnimation());

mFlipper.showPrevious();

} else {

mCurrentLayoutState++;

mFlipper.setInAnimation(inFromRightAnimation());

mFlipper.setOutAnimation(outToLeftAnimation());

mFlipper.showNext();

}



}

;

}



/**

* 定义从右侧进入的动画效果

* @return

*/

protected Animation inFromRightAnimation() {

Animation inFromRight = new TranslateAnimation(

Animation.RELATIVE_TO_PARENT, +1.0f,

Animation.RELATIVE_TO_PARENT, 0.0f,

Animation.RELATIVE_TO_PARENT, 0.0f,

Animation.RELATIVE_TO_PARENT, 0.0f);

inFromRight.setDuration(500);

inFromRight.setInterpolator(new AccelerateInterpolator());

return inFromRight;

}



/**

* 定义从左侧退出的动画效果

* @return

*/

protected Animation outToLeftAnimation() {

Animation outtoLeft = new TranslateAnimation(

Animation.RELATIVE_TO_PARENT, 0.0f,

Animation.RELATIVE_TO_PARENT, -1.0f,

Animation.RELATIVE_TO_PARENT, 0.0f,

Animation.RELATIVE_TO_PARENT, 0.0f);

outtoLeft.setDuration(500);

outtoLeft.setInterpolator(new AccelerateInterpolator());

return outtoLeft;

}



/**

* 定义从左侧进入的动画效果

* @return

*/

protected Animation inFromLeftAnimation() {

Animation inFromLeft = new TranslateAnimation(

Animation.RELATIVE_TO_PARENT, -1.0f,

Animation.RELATIVE_TO_PARENT, 0.0f,

Animation.RELATIVE_TO_PARENT, 0.0f,

Animation.RELATIVE_TO_PARENT, 0.0f);

inFromLeft.setDuration(500);

inFromLeft.setInterpolator(new AccelerateInterpolator());

return inFromLeft;

}



/**

* 定义从右侧退出时的动画效果

* @return

*/

protected Animation outToRightAnimation() {

Animation outtoRight = new TranslateAnimation(

Animation.RELATIVE_TO_PARENT, 0.0f,

Animation.RELATIVE_TO_PARENT, +1.0f,

Animation.RELATIVE_TO_PARENT, 0.0f,

Animation.RELATIVE_TO_PARENT, 0.0f);

outtoRight.setDuration(500);

outtoRight.setInterpolator(new AccelerateInterpolator());

return outtoRight;

}



public boolean onDown(MotionEvent e) {

// TODO Auto-generated method stub

return false;

}



/*

* 用户按下触摸屏、快速移动后松开即触发这个事件

* e1：第1个ACTION_DOWN MotionEvent

* e2：最后一个ACTION_MOVE MotionEvent

* velocityX：X轴上的移动速度，像素/秒

* velocityY：Y轴上的移动速度，像素/秒

* 触发条件 ：

* X轴的坐标位移大于FLING_MIN_DISTANCE，且移动速度大于FLING_MIN_VELOCITY个像素/秒

*/

public boolean onFling(MotionEvent e1, MotionEvent e2, float velocityX,

float velocityY) {

if (e1.getX() – e2.getX() > FLING_MIN_DISTANCE

&& Math.abs(velocityX) > FLING_MIN_VELOCITY) {

// 当像左侧滑动的时候

//设置View进入屏幕时候使用的动画

mFlipper.setInAnimation(inFromRightAnimation());

//设置View退出屏幕时候使用的动画

mFlipper.setOutAnimation(outToLeftAnimation());

mFlipper.showNext();

} else if (e2.getX() – e1.getX() > FLING_MIN_DISTANCE

&& Math.abs(velocityX) > FLING_MIN_VELOCITY) {

// 当像右侧滑动的时候

mFlipper.setInAnimation(inFromLeftAnimation());

mFlipper.setOutAnimation(outToRightAnimation());

mFlipper.showPrevious();

}

return false;

}



public void onLongPress(MotionEvent e) {

// TODO Auto-generated method stub



}



public boolean onScroll(MotionEvent e1, MotionEvent e2, float distanceX,

float distanceY) {

return false;

}



public void onShowPress(MotionEvent e) {

// TODO Auto-generated method stub



}



public boolean onSingleTapUp(MotionEvent e) {

// TODO Auto-generated method stub

return false;

}

public boolean onTouch(View v, MotionEvent event) {

// 一定要将触屏事件交给手势识别类去处理（自己处理会很麻烦的）

return mGestureDetector.onTouchEvent(event);

}

}
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