ViewPager的fakeDragBy()或setCurrentItem()不能捕捉到当前项目 [英] ViewPager's fakeDragBy() or setCurrentItem() doesn't snap to current item
问题描述
已解决.请参阅标记为正确答案的答案以及我的评论.可以在必要时发布示例代码
Resolved. See answer marked as correct along with my comments. Can post example code if necessary
我正在使用 VelocityViewPager 来实现转移"行为.有一种已知的行为，即如果将页面拖动一定量，页面将无法对齐.我正在努力解决这个问题，但收效甚微...
I'm using the VelocityViewPager to implement a "fling" behavior. There is a known behavior with it where the page doesn't snap if you drag it by a certain amount. I'm trying to get around it with little success...
尝试1
通过使用setCurrentItem，我可以使快照操作正常工作.需要注意的是，仅当我在当前页面之前或之后的项目上调用该函数时，该快照才会捕捉到，例如setCurrentItem(getCurrentItem()+1)
I can get the snap action to work correctly by using setCurrentItem. The caveat is that it only snaps if I call the function on an item before or after the current page, for example setCurrentItem(getCurrentItem()+1)
因此，此解决方案有效，但是如果我必须将当前项目设置得比他们期望的要多，则会给用户带来糟糕的用户体验.
So this solution works, but it gives the user a bad user experience if I have to set the current item further than they expect it to.
有人对我如何称呼setCurrentItem(getCurrentItem())并使它实际上具有动画/滚动/捕捉效果有任何建议吗? .消息来源暗示应该这样做. r7代码似乎总是调用滚动功能.
Does anyone have any advice on how I can call setCurrentItem(getCurrentItem()) and have it actually animate/scroll/snap? The source implies that it should. The r7 code seems to always call the scroll function.
尝试2
作为另一个测试，我进行了许多fakeDragBy(1)调用来拖动ViewPager，以为它会在达到一定阈值后迅速捕捉，但事实并非如此. 是什么导致ViewPager无法捕捉?
As another test, I did many fakeDragBy(1) calls to drag the ViewPager thinking that it would snap after it reached a certain threshold, but that wasn't the case. What's preventing the ViewPager from snapping?
如果有兴趣，下面是重现此代码的代码.我使用相同的 VelocityViewPager 代码进行了以下更改
Below is code to reproduce this, if you're interested. I used the same VelocityViewPager code with the following changes
VelocityViewPager.java
public class VelocityViewPager extends ViewPager implements GestureDetector.OnGestureListener {
...
@Override
public boolean onTouchEvent(MotionEvent event) {
// give all the events to the gesture detector. I'm returning true here so the viewpager doesn't
// get any events at all, I'm sure you could adjust this to make that not true.
mGestureDetector.onTouchEvent(event);
if (event.getAction() == MotionEvent.ACTION_UP) {
setCurrentItem(getCurrentItem(), true);
Log.d("VelocityViewPager", "Setting to item " + getCurrentItem());
}
return true;
}
....
}
MainActivity.java
package com.example.velocityviewpager;
import android.graphics.Color;
import android.os.Bundle;
import android.app.Activity;
import android.support.v4.view.PagerAdapter;
import android.view.Gravity;
import android.view.Menu;
import android.view.View;
import android.view.ViewGroup;
import android.widget.TextView;
public class MainActivity extends Activity {
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
VelocityViewPager pager = (VelocityViewPager)findViewById(R.id.view);
PagerAdapter adapter = new PagerAdapter() {
@Override
public int getCount() {
return 20;
}
@Override
public Object instantiateItem(ViewGroup container, int position) {
TextView view = new TextView(MainActivity.this);
view.setText("Item "+position);
view.setGravity(Gravity.CENTER);
view.setBackgroundColor(Color.argb(255, position * 10, position * 10, position * 10));
view.setTextColor(Color.argb(255, 200, 200, 200));
container.addView(view);
return view;
}
@Override
public void destroyItem(ViewGroup container, int position, Object object) {
container.removeView((View)object);
}
@Override
public boolean isViewFromObject(View view, Object o) {
return (view == o);
}
};
pager.setAdapter(adapter);
adapter.notifyDataSetChanged();
pager.setOffscreenPageLimit(3);
pager.setCurrentItem(0, true);
}
@Override
public boolean onCreateOptionsMenu(Menu menu) {
// Inflate the menu; this adds items to the action bar if it is present.
getMenuInflater().inflate(R.menu.main, menu);
return true;
}
}
activity_main.xml
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:paddingLeft="@dimen/activity_horizontal_margin"
android:paddingRight="@dimen/activity_horizontal_margin"
android:paddingTop="@dimen/activity_vertical_margin"
android:paddingBottom="@dimen/activity_vertical_margin"
tools:context=".MainActivity">
<view
android:layout_width="300dip"
android:layout_height="300dip"
class="com.example.velocityviewpager.VelocityViewPager"
android:id="@+id/view"
android:layout_alignParentTop="true"
android:layout_alignParentLeft="true"
android:layout_alignParentRight="true"/>
</RelativeLayout>
推荐答案
我找到了一种解决方法.我跟踪以前做过的动作，并且当MotionEvent.ACTION_UP发生时，我会触发新的猛冲.我不确定，如果这种方式在逻辑上是正确的(这是正确的方向吗?对于新的猛击来说，这是否是一个好的速度?)，但是我对其进行了测试，并且它的工作原理是:
I have found a workaround. I track what movement was done previously, and when a MotionEvent.ACTION_UP occurs I trigger a new fling. I am not sure, if it's logically correct this way (is this the good direction? and is this a good velocity for a new fling?), but I tested it, and it works:
private boolean isLeftDirection = false;
@Override
public boolean onTouchEvent(MotionEvent event) {
// give all the events to the gesture detector. I'm returning true here
// so the viewpager doesn't
// get any events at all, I'm sure you could adjust this to make that
// not true.
if (event.getAction() == MotionEvent.ACTION_UP) {
int id = getCurrentItem();
setCurrentItem(id, true);
if (isLeftDirection){
mFlingRunnable.startUsingVelocity((int) 1);
} else {
mFlingRunnable.startUsingVelocity((int) -1);
}
}
mGestureDetector.onTouchEvent(event);
return true;
}
@Override
public boolean onScroll(MotionEvent e1, MotionEvent e2, float distX,
float distY) {
trackMotion(-distX);
if (distX > 0){
isLeftDirection = true;}
else{
isLeftDirection = false;
}
return false;
}
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