Android移动开发-手势事件处理MotionEvent的实现

手势事件处理MotionEvent是智能手机的一大特性，即可用于信息输出（显示界面）又可用于输入（检测用户的触摸行为）。为了方便开发者使用，Android已经自动识别特定的几种触摸手势，包括按钮的点击事件OnClickListener、长按事件OnLongClickListener、滚动视图ScrollView的上下滚动事件、翻页视图ViewPager的左右翻页事件等。
其中dispatchTouchEvent、onInterceptTouchEvent和onTouchEvent的输入参数都是手势事件MotionEvent，其中包含触摸动作的所有信息，各种手势操作都得到MotionEvent中获取信息并进行判断处理。

以下是演示单点触摸的代码实现：

• layout/activity_touch_single.xml界面布局代码如下：

package com.fukaimei.touchevent;

import java.util.Date;

import android.os.Bundle;
import android.support.v7.app.AppCompatActivity;
import android.view.MotionEvent;
import android.widget.TextView;

public class TouchSingleActivity extends AppCompatActivity {
    private TextView tv_touch;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_touch_single);
        tv_touch = (TextView) findViewById(R.id.tv_touch);
    }

    @Override
    public boolean onTouchEvent(MotionEvent event) {
        // 从开机到现在的毫秒数
        int seconds = (int) (event.getEventTime() / 1000);
        int hour = seconds / 3600;
        int minute = seconds % 3600 / 60;
        int second = seconds % 60;
        Date date = new Date(event.getEventTime());
        String desc = String.format("动作发生时间：开机距离现在%02d:%02d:%02d",
                hour, minute, second);
        desc = String.format("%s\n动作名称是：", desc);
        int action = event.getAction();
        if (action == event.ACTION_DOWN) {
            desc = String.format("%s按下", desc);
        } else if (action == event.ACTION_MOVE) {
            desc = String.format("%s移动", desc);
        } else if (action == event.ACTION_UP) {
            desc = String.format("%s提起", desc);
        } else if (action == event.ACTION_CANCEL) {
            desc = String.format("%s取消", desc);
        }
        desc = String.format("%s\n动作发生位置是：横坐标%f，纵坐标%f",
                desc, event.getX(), event.getY());
        tv_touch.setText(desc);
        return super.onTouchEvent(event);
    }

}

• TouchSingleActivity.java逻辑代码如下：

package com.fukaimei.touchevent;

import java.util.Date;

import android.os.Bundle;
import android.support.v7.app.AppCompatActivity;
import android.view.MotionEvent;
import android.widget.TextView;

public class TouchSingleActivity extends AppCompatActivity {
    private TextView tv_touch;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_touch_single);
        tv_touch = (TextView) findViewById(R.id.tv_touch);
    }

    @Override
    public boolean onTouchEvent(MotionEvent event) {
        // 从开机到现在的毫秒数
        int seconds = (int) (event.getEventTime() / 1000);
        int hour = seconds / 3600;
        int minute = seconds % 3600 / 60;
        int second = seconds % 60;
        Date date = new Date(event.getEventTime());
        String desc = String.format("动作发生时间：开机距离现在%02d:%02d:%02d",
                hour, minute, second);
        desc = String.format("%s\n动作名称是：", desc);
        int action = event.getAction();
        if (action == event.ACTION_DOWN) {
            desc = String.format("%s按下", desc);
        } else if (action == event.ACTION_MOVE) {
            desc = String.format("%s移动", desc);
        } else if (action == event.ACTION_UP) {
            desc = String.format("%s提起", desc);
        } else if (action == event.ACTION_CANCEL) {
            desc = String.format("%s取消", desc);
        }
        desc = String.format("%s\n动作发生位置是：横坐标%f，纵坐标%f",
                desc, event.getX(), event.getY());
        tv_touch.setText(desc);
        return super.onTouchEvent(event);
    }

}

• Demo程序运行效果界面截图如下：

除了单点触摸外，智能手机还普通支持多点触控，即响应两个及以上手指同时按压屏幕。多点触控可用于操纵图像的缩放与旋转操作，以及需要多点处理的游戏界面等。

下面是演示多点触控的页面代码：

• layout/activity_touch_multiple.xml界面布局代码如下：

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical"
    android:padding="5dp">

    <TextView
        android:id="@+id/tv_touch_main"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:text="这里显示主要点触摸结果"
        android:textColor="@color/black"
        android:textSize="17sp" />

    <TextView
        android:id="@+id/tv_touch_secondary"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:text="这里显示次要点触摸结果"
        android:textColor="@color/black"
        android:textSize="17sp" />

</LinearLayout>

• TouchMultipleActivity.java逻辑代码如下：

package com.fukaimei.touchevent;

import java.util.Date;

import android.os.Bundle;
import android.support.v7.app.AppCompatActivity;
import android.view.MotionEvent;
import android.widget.TextView;

public class TouchMultipleActivity extends AppCompatActivity {
    private TextView tv_touch_main;
    private TextView tv_touch_secondary;
    private boolean bSecondaryPressed = false;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_touch_multiple);
        tv_touch_main = (TextView) findViewById(R.id.tv_touch_main);
        tv_touch_secondary = (TextView) findViewById(R.id.tv_touch_secondary);
    }

    @Override
    public boolean onTouchEvent(MotionEvent event) {
        int seconds = (int) (event.getEventTime() / 1000);
        int hour = seconds / 3600;
        int minute = seconds % 3600 / 60;
        int second = seconds % 60;
        Date date = new Date(event.getEventTime());
        String desc_main = String.format("主要动作发生时间：开机距离现在%02d:%02d:%02d\n%s",
                hour, minute, second, "主要动作名称是：");
        String desc_secondary = "";
        int action = event.getAction() & MotionEvent.ACTION_MASK;
        if (action == event.ACTION_DOWN) {
            desc_main = String.format("%s按下", desc_main);
        } else if (action == event.ACTION_MOVE) {
            desc_main = String.format("%s移动", desc_main);
            if (bSecondaryPressed == true) {
                desc_secondary = String.format("%s次要动作名称是：移动", desc_secondary);
            }
        } else if (action == event.ACTION_UP) {
            desc_main = String.format("%s提起", desc_main);
        } else if (action == event.ACTION_CANCEL) {
            desc_main = String.format("%s取消", desc_main);
        } else if (action == event.ACTION_POINTER_DOWN) {
            bSecondaryPressed = true;
            desc_secondary = String.format("%s次要动作名称是：按下", desc_secondary);
        } else if (action == event.ACTION_POINTER_UP) {
            bSecondaryPressed = false;
            desc_secondary = String.format("%s次要动作名称是：提起", desc_secondary);
        }
        desc_main = String.format("%s\n主要动作发生位置是：横坐标%f，纵坐标%f",
                desc_main, event.getX(), event.getY());
        tv_touch_main.setText(desc_main);
        if (bSecondaryPressed == true || desc_secondary.length() > 0) {
            desc_secondary = String.format("%s\n次要动作发生位置是：横坐标%f，纵坐标%f",
                    desc_secondary, event.getX(1), event.getY(1));
            tv_touch_secondary.setText(desc_secondary);
        }
        return super.onTouchEvent(event);
    }

}

• Demo程序运行效果界面截图如下：

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