Android Check Long Press Helper

基本思想:在Down事件中向UI线程塞入一个定时任务,如果在定时时间终了前任务没有被取消,就认为是一个长按事件。

/*
 * Copyright (C) 2012 The Android Open Source Project
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package com.android.keyguard;

import android.view.MotionEvent;
import android.view.View;
import android.view.ViewConfiguration;

public class CheckLongPressHelper {
    private View mView;
    private boolean mHasPerformedLongPress;
    private CheckForLongPress mPendingCheckForLongPress;
    private float mDownX, mDownY;
    private int mLongPressTimeout;
    private int mScaledTouchSlop;

    class CheckForLongPress implements Runnable {
        public void run() {
            if ((mView.getParent() != null) && mView.hasWindowFocus()
                    && !mHasPerformedLongPress) {
                if (mView.performLongClick()) {
                    mView.setPressed(false);
                    mHasPerformedLongPress = true;
                }
            }
        }
    }

    public CheckLongPressHelper(View v) {
        mScaledTouchSlop = ViewConfiguration.get(v.getContext()).getScaledTouchSlop();
        mLongPressTimeout = ViewConfiguration.getLongPressTimeout();
        mView = v;
    }

    public void postCheckForLongPress(MotionEvent ev) {
        mDownX = ev.getX();
        mDownY = ev.getY();
        mHasPerformedLongPress = false;

        if (mPendingCheckForLongPress == null) {
            mPendingCheckForLongPress = new CheckForLongPress();
        }
        mView.postDelayed(mPendingCheckForLongPress, mLongPressTimeout);
    }

    public void onMove(MotionEvent ev) {
        float x = ev.getX();
        float y = ev.getY();
        boolean xMoved = Math.abs(mDownX - x) > mScaledTouchSlop;
        boolean yMoved = Math.abs(mDownY - y) > mScaledTouchSlop;

        if (xMoved || yMoved) {
            cancelLongPress();
        }
    }

    public void cancelLongPress() {
        mHasPerformedLongPress = false;
        if (mPendingCheckForLongPress != null) {
            mView.removeCallbacks(mPendingCheckForLongPress);
            mPendingCheckForLongPress = null;
        }
    }

    public boolean hasPerformedLongPress() {
        return mHasPerformedLongPress;
    }
}

ref:Android-4.4/frameworks/base/packages/Keyguard/src/com/android/keyguard/CheckLongPressHelpe

在 Android Makefile 中使用通配符

LOCAL_PATH := $(call my-dir)
include $(CLEAR_VARS)
LOCAL_MODULE    := Hello
LOCAL_SRC_FILES := $(wildcard $(LOCAL_PATH)/*.c)
include $(BUILD_STATIC_LIBRARY)

Android FragmentPagerAdapter Demo

package com.example.sijiewang.testviewpager;

import android.os.Bundle;
import android.support.v4.app.Fragment;
import android.support.v4.app.FragmentActivity;
import android.support.v4.app.FragmentManager;
import android.support.v4.app.FragmentPagerAdapter;
import android.support.v4.view.ViewPager;
import java.util.ArrayList;

public class MainActivity extends FragmentActivity {
    private ViewPager mAlarmCreateViewPager;
    private Fragment mFragmentOne;
    private Fragment mFragmentTwo;
    private ArrayList<Fragment> mFragmentList;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        mFragmentList = new ArrayList<Fragment>(2);
        mFragmentOne = new mFragmentOne();
        mFragmentList.add(mFragmentOne);
        mFragmentTwo = new mFragmentTwo();
        mFragmentList.add(mFragmentTwo);

        mAlarmCreateViewPager = (ViewPager) findViewById(R.id.viewpager);
        mAlarmCreateViewPager.setAdapter(new FragmentPagerAdapterDemo(getSupportFragmentManager()));
    }

    class FragmentPagerAdapterDemo extends FragmentPagerAdapter {

        public PagerAdapterDemo(FragmentManager fm) {
            super(fm);
        }

        @Override
        public Fragment getItem(int arg0) {
            return mFragmentList.get(arg0);
        }

        @Override
        public int getCount() {
            return mFragmentList.size();
        }

    }
}

一些特性:1.当使用FragmentPagerAdapter时,所有的Fragment都不会被销毁,但是Fragment本身生命周期中跟UI相关的方法在每次显示状态改变的时候都会被重复调用。2.由于第一条中的原因,FragmentPagerAdapter不适合大量数据的展示。当有大量数据时,GOOGLE推荐使用FragmentStatePagerAdapter。

Android PagerAdapter Demo

package com.example.sijiewang.testviewpager;

import android.app.Activity;
import android.os.Bundle;
import android.support.v4.view.PagerAdapter;
import android.support.v4.view.ViewPager;
import android.view.LayoutInflater;
import android.view.View;

import java.util.ArrayList;

public class MainActivity extends Activity {
    private ViewPager mViewPager;
    private ArrayList<View> mViewList;
    private LayoutInflater mLayoutInflater;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        mLayoutInflater = getLayoutInflater();

        mViewList = new ArrayList<View>(4);
        mViewList.add(mLayoutInflater.inflate(R.layout.page1, null));
        mViewList.add(mLayoutInflater.inflate(R.layout.page2, null));
        mViewList.add(mLayoutInflater.inflate(R.layout.page3, null));
        mViewList.add(mLayoutInflater.inflate(R.layout.page4, null));

        mViewPager = (ViewPager) findViewById(R.id.viewpager);
        mViewPager.setAdapter(new PagerAdapterDemo());
    }

    class PagerAdapterDemo extends PagerAdapter {

        @Override
        public int getCount() {
            return mViewList.size();
        }

        @Override
        public Object instantiateItem(View container, int position) {
            ((ViewPager) container).addView(mViewList.get(position), 0);
            return mViewList.get(position);
        }

        @Override
        public void destroyItem(View container, int position, Object object) {
            ((ViewPager)container).removeView(mViewList.get(position));
        }

        @Override
        public boolean isViewFromObject(View view, Object obj) {
            return view == obj;
        }
    }

}

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">

    <android.support.v4.view.ViewPager
        android:id="@+id/viewpager"
        android:layout_width="match_parent"
        android:layout_height="match_parent" />

</RelativeLayout>

一些特性:PagerAdapter始终会保持当前和下一个Page可用,销毁前一个Page 。

Android 绘制透明矩形

    Paint paint;
    Rect  spaceRect;

    spaceRect = new Rect();
    spaceRect.set(left, top, right, bottom);

    paint.setStyle(Paint.Style.FILL);
    paint.setAlpha(0);

    c.drawRect(spaceRect, paint);