Android笔记

​ ——自定义缩放控件
【若对该知识点有更多想了解的，欢迎私信博主~~】

Drawable类的介绍:https://blog.csdn.net/feather_wch/article/details/79124608

Math类的介绍：https://blog.csdn.net/a22422931/article/details/52129417

制作：

package com.example.sirl.daypractice.T1;import android.content.Context;
import android.graphics.Canvas;
import android.graphics.drawable.Drawable;
import android.support.v7.widget.AppCompatImageView;
import android.util.AttributeSet;
import android.util.Log;
import android.view.MotionEvent;import java.util.Calendar;public class MyView2 extends AppCompatImageView {private Drawable drawable;//画笔private double old = 0;private float x = 1.0f, y = 1.0f;private float downx, downy;private float movex = 1.0f, movey = 1.0f;int state = 0;//点击次数Long time;//点击事件（用于判断双击）//重写构造函数public MyView2(Context context, AttributeSet attrs) {super(context, attrs);drawable = getDrawable();//获取画笔}//制作控件@Overrideprotected void onDraw(Canvas canvas) {//画布大小(X轴放大比例，Y轴放大比例，中心点横坐标，中心点纵坐标)canvas.scale(x, y, getWidth() / 2, getHeight() / 2);//画布当前位置（X轴偏移量，Y轴偏移量）canvas.translate(movex, movey);//保存画布canvas.save();super.onDraw(canvas);}//触摸事件@Overridepublic boolean onTouchEvent(MotionEvent event) {//获取当前日期（用于判断双击）Calendar calendar = Calendar.getInstance();//如果触摸点为1个（双击放大和移动画布）if (event.getPointerCount() == 1) {//如果为按下事件if (event.getAction() == event.ACTION_DOWN) {downx = event.getX() - movex;downy = event.getY() - movey;//状态为0时if (state == 0) {state = 1;time = calendar.getTime().getTime();//第一次纪录时间}//状态为1时else if (state == 1) {//如果第二次点击时间与第一次小于0.3s，则为双击if (calendar.getTime().getTime() - time < 300) {x = 2.0f;//横向放大2倍y = 2.0f;//纵向放大2倍state = 2;invalidate();//更新画布}//如果时间大于0.3s，则为单击else {state = 0;}}//状态为2时（用于双击放大后仍可以移动）else if (state==2){state=3;}}//如果为移动事件else if (event.getAction() == event.ACTION_MOVE) {movex = event.getX() - downx;movey = event.getY() - downy;invalidate();}//如果为松开事件else if (event.getAction() == event.ACTION_UP) {//取消双击放大if (state == 3) {x = 1.0f;y = 1.0f;state = 0;invalidate();}}}//双指方法else if (event.getPointerCount() > 1) {float x0 = event.getX(0);//手指1的横坐标float x1 = event.getX(1);//手指2的横坐标float y0 = event.getY(0);//手指1的纵坐标float y1 = event.getY(1);//手指2的纵坐标double news = Math.sqrt(Math.pow(x0 - x1, 2) + Math.pow(y0 - y1, 2));//当前双指距离//如果双指移动if (event.getAction() == event.ACTION_MOVE) {//如果当前距离大于曾经距离并且放大比例小于4倍if (news > old && x < 4) {x += 0.01;y += 0.01;}//如果当前距离小于曾经距离并且缩小比例大于4倍else if (news < old && x > 0.05) {x -= 0.01;y -= 0.01;}//更新画布invalidate();}//松开后纪录双指距离，用于下次判断old = news;}return true;}
}

使用：

1.在Activity里直接布局

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"xmlns:app="http://schemas.android.com/apk/res-auto"xmlns:tools="http://schemas.android.com/tools"android:layout_width="match_parent"android:layout_height="match_parent"android:background="#fff"android:orientation="vertical"tools:context=".work7.Main7Activity"><com.example.sirl.demo0711.work7.MyViewandroid:id="@+id/mv"android:layout_width="match_parent"android:layout_height="match_parent" /></LinearLayout>

2.因为该控件继承ImageView,直接放入图片即可

public class Main7Activity extends AppCompatActivity {MyView myView;@Overrideprotected void onCreate(Bundle savedInstanceState) {super.onCreate(savedInstanceState);setContentView(R.layout.activity_main7);myView=findViewById(R.id.mv);myView.setImageResource(R.mipmap.ic_launcher);}
}