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Android自定义View实现可拖拽缩放的矩形框的方法

这篇文章主要讲解了Android自定义View实现可拖拽缩放的矩形框的方法，内容清晰明了，对此有兴趣的小伙伴可以学习一下，相信大家阅读完之后会有帮助。

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在开发项目中，需要一个矩形框来实现截屏功能，并且还需要可以任意拖拽和缩放，这就需要自定义View来实现了，具体功能如下：

1.自定义View

package com.xinrui.screenshot.view;

import android.content.Context;
import android.graphics.Canvas;
import android.graphics.Color;
import android.graphics.Paint;
import android.graphics.RectF;
import android.support.annotation.Nullable;
import android.util.AttributeSet;
import android.util.Log;
import android.util.TypedValue;
import android.view.MotionEvent;
import android.view.View;

public class CropRectView extends View {
 
 // 绘制 损害框和损害名称
 private Paint mPaint;
 private RectF mRectF;
 
 // 边缘字体
// private BorderedText mBorderedText;
 
 // 标题 或 名字
 private String mTitle;
 // 概率
 private float mConfidence;
 
 // 矩形框 corner 的角度：直角、圆角
 private int mCornerAngle;
 
 //直角 默认
 public static final int RIGHT_CORNER = 0;
 //圆角
 public static final int ROUND_CORNER = 1;
 
 // Remove Rect
 private int MODE;
 private static final int MODE_OUTSIDE = 0x000000aa;/*170*/
 private static final int MODE_INSIDE = 0x000000bb;/*187*/
 private static final int MODE_POINT = 0X000000cc;/*204*/
 private static final int MODE_ILLEGAL = 0X000000dd;/*221*/
 
 private float startX;/*start X location*/
 private float startY;/*start Y location*/
 private float endX;/*end X location*/
 private float endY;/*end Y location*/
 
 private float currentX;/*X coordinate values while finger press*/
 private float currentY;/*Y coordinate values while finger press*/
 
 private float memoryX;/*the last time the coordinate values of X*/
 private float memoryY;/*the last time the coordinate values of Y*/
 
 private float mCoverWidth;/*width of selection box*/
 private float mCoverHeight;/*height of selection box*/
 
 private static final int ACCURACY = 100;/*touch accuracy*/
 private int pointPosition;/*vertex of a rectangle*/
 
 private static final float minWidth = 100.0f;/*the minimum width of the rectangle*/
 private static final float minHeight = 200.0f;/*the minimum height of the rectangle*/
 
 private onLocationListener mLocationListener;/*listen to the Rect */
 
 private static final float EDGE_WIDTH = 1.8f;
 
 public MoveAndCropRectView(Context context) {
  this(context, null);
 }
 
 public MoveAndCropRectView(Context context, @Nullable AttributeSet attrs) {
  this(context, attrs, 0);
 }
 
 public MoveAndCropRectView(Context context, @Nullable AttributeSet attrs, int defStyleAttr) {
  super(context, attrs, defStyleAttr);
  initDatas(context);
 }
 
 private void initDatas(Context context) {
  mPaint = new Paint();
  mRectF = new RectF();
 
  //画笔设置空心
  mPaint.setStyle(Paint.Style.STROKE);
  mPaint.setColor(Color.WHITE);
  mPaint.setStrokeWidth(2);
  mPaint.setAntiAlias(true);
 
//  float textSizePx = TypedValue.applyDimension(TypedValue.COMPLEX_UNIT_DIP,
//    18.0f, context.getResources().getDisplayMetrics());
//  mBorderedText = new BorderedText(textSizePx);
  currentX = 0;
  currentY = 0;
 }
 
 private boolean firstDraw = true;
 
 @Override
 protected void onDraw(Canvas canvas) {
  super.onDraw(canvas);
 
//  switch (mCornerAngle) {
//   case RIGHT_CORNER:// 绘制 损害框(直角矩形框)
//    drawRect(canvas);
//    break;
//   case ROUND_CORNER:// 绘制 损害框(圆角矩形框)
//    drawRoundRect(canvas);
//    break;
//  }
 
  if (firstDraw) {
   firstDraw = false;
   startX = mRectF.left;
   startY = mRectF.top;
   endX = mRectF.right;
   endY = mRectF.bottom;
 
   mCoverWidth = mRectF.width();
   mCoverHeight = mRectF.height();
  }
 
 
  if (mLocationListener != null) {
   mLocationListener.locationRect(startX, startY, endX, endY);
  }
 
//  LogUtils.d("onDraw -- startX: " + startX);
 
  canvas.drawLine(startX - EDGE_WIDTH, startY - EDGE_WIDTH,
    endX + EDGE_WIDTH, startY - EDGE_WIDTH, mPaint);/*top 上边框-*/
  canvas.drawLine(startX - EDGE_WIDTH, endY + EDGE_WIDTH,
    endX + EDGE_WIDTH, endY + EDGE_WIDTH, mPaint);/*bottom -*/
  canvas.drawLine(startX - EDGE_WIDTH, startY - EDGE_WIDTH,
    startX - EDGE_WIDTH, endY + EDGE_WIDTH, mPaint);/*left |*/
  canvas.drawLine(endX + EDGE_WIDTH, startY - EDGE_WIDTH,
    endX + EDGE_WIDTH, endY + EDGE_WIDTH, mPaint);/*right |*/
 
  // 绘制名称 和 概率
//  final String labelString =
//    !TextUtils.isEmpty(mTitle)
//      ? String.format("%s %.2f", mTitle, (100 * mConfidence))
//      : String.format("%.2f", (100 * mConfidence));
//
//  // 在 直角矩形框 上写字
//  mBorderedText.drawText(canvas,
//    startX,
//    startY, labelString + "%",
//    mPaint);
 }
 
 @SuppressWarnings("NullableProblems")
 @Override
 public boolean onTouchEvent(MotionEvent event) {
  switch (event.getAction()) {
   case MotionEvent.ACTION_DOWN:
    memoryX = event.getX();
    memoryY = event.getY();
    checkMode(memoryX, memoryY);
    break;
   case MotionEvent.ACTION_MOVE: {
    currentX = event.getX();
    currentY = event.getY();
    switch (MODE) {
     case MODE_ILLEGAL:
      recoverFromIllegal(currentX, currentY);
      postInvalidate();
      break;
     case MODE_OUTSIDE:
      //do nothing;
      break;
     case MODE_INSIDE://拖动
      moveByTouch(currentX, currentY);
      postInvalidate();
      break;
     default:
      /*MODE_POINT*/
      moveByPoint(currentX, currentY);
      postInvalidate();
      break;
    }
   }
   break;
   case MotionEvent.ACTION_UP:
//    mPaint.setColor(getContext().getResources().getColor(R.color.orange));
    postInvalidate();
    break;
   default:
    break;
  }
  return true;
 }
 
 /*点击顶点附近时的缩放处理*/
 @SuppressWarnings("SuspiciousNameCombination")
 private void moveByPoint(float bx, float by) {
//  LogUtils.d("moveByPoint");
  switch (pointPosition) {
   case 0:/*left-up*/
    mCoverWidth = Math.abs(endX - bx);
    mCoverHeight = Math.abs(endY - by);
    //noinspection SuspiciousNameCombination
    if (!checkLegalRect(mCoverWidth, mCoverHeight)) {
     MODE = MODE_ILLEGAL;
    } else {
     refreshLocation(bx, by, endX, endY);
    }
    break;
   case 1:/*right-up*/
    mCoverWidth = Math.abs(bx - startX);
    mCoverHeight = Math.abs(endY - by);
    if (!checkLegalRect(mCoverWidth, mCoverHeight)) {
     MODE = MODE_ILLEGAL;
    } else {
     refreshLocation(startX, by, bx, endY);
    }
    break;
   case 2:/*left-down*/
    mCoverWidth = Math.abs(endX - bx);
    mCoverHeight = Math.abs(by - startY);
    if (!checkLegalRect(mCoverWidth, mCoverHeight)) {
     MODE = MODE_ILLEGAL;
    } else {
     refreshLocation(bx, startY, endX, by);
    }
    break;
   case 3:/*right-down*/
    mCoverWidth = Math.abs(bx - startX);
    mCoverHeight = Math.abs(by - startY);
    if (!checkLegalRect(mCoverWidth, mCoverHeight)) {
     MODE = MODE_ILLEGAL;
    } else {
     refreshLocation(startX, startY, bx, by);
    }
    break;
   default:
    break;
  }
 }
 
 /*刷新矩形的坐标*/
 private void refreshLocation(float isx, float isy, float iex, float iey) {
  this.startX = isx;
  this.startY = isy;
  this.endX = iex;
  this.endY = iey;
 
  mCoverWidth = endX - startX;
  mCoverHeight = endY - startY;

 }
 
 /*检测矩形是否达到最小值*/
 private boolean checkLegalRect(float cHeight, float cWidth) {
  return (cHeight > minHeight && cWidth > minWidth);
 }
 
 /*从非法状态恢复，这里处理的是达到最小值后能拉伸放大*/
 private void recoverFromIllegal(float rx, float ry) {
  if ((rx > startX && ry > startY) && (rx < endX && ry < endY)) {
   MODE = MODE_ILLEGAL;
  } else {
   MODE = MODE_POINT;
  }
 }

 /**
  * 判断点在矩形的什么位置
  * @param cx
  * @param cy
  */
 private void checkMode(float cx, float cy) {
  if (cx > startX && cx < endX && cy > startY && cy < endY) {
   MODE = MODE_INSIDE;//矩形内部
  } else if (nearbyPoint(cx, cy) < 4) {
   MODE = MODE_POINT;//矩形点上
  } else {
   MODE = MODE_OUTSIDE;//矩形外部
  }
 }
 
 /*矩形随手指移动*/
 private void moveByTouch(float mx, float my) {/*move center point*/
  float dX = mx - memoryX;
  float dY = my - memoryY;

  startX += dX;
  startY += dY;
  if(startX<=0){
   startX=0;
  }
  if(startY<=0){
   startY=0;
  }
  endX = startX + mCoverWidth;
  endY = startY + mCoverHeight;
  if(endX>=1920){
   endX=1920;
   startX=endX-mCoverWidth;
  }
  if(endY>=1080){
   endY=1080;
   startY=endY-mCoverHeight;
  }
  memoryX = mx;
  memoryY = my;
 }
 
 /*判断点(inX,inY)是否靠近矩形的4个顶点*/
 private int nearbyPoint(float floatX, float floatY) {
  if ((Math.abs(startX - floatX) <= ACCURACY && (Math.abs(floatY - startY) <= ACCURACY))) {/*left-up angle*/
   pointPosition = 0;
   return 0;
  }
  if ((Math.abs(endX - floatX) <= ACCURACY && (Math.abs(floatY - startY) <= ACCURACY))) {/*right-up angle*/
   pointPosition = 1;
   return 1;
  }
  if ((Math.abs(startX - floatX) <= ACCURACY && (Math.abs(floatY - endY) <= ACCURACY))) {/*left-down angle*/
   pointPosition = 2;
   return 2;
  }
  if ((Math.abs(endX - floatX) <= ACCURACY && (Math.abs(floatY - endY) <= ACCURACY))) {/*right-down angle*/
   pointPosition = 3;
   return 3;
  }
  pointPosition = 100;
  return 100;
 }
 
 // 设置矩形框
 public void setRectF(RectF rectf) {
  this.mRectF = rectf;
 }
 
 public void setTitle(String title) {
  mTitle = title;
 }
 
 public void setConfidence(float confidence) {
  mConfidence = confidence;
 }
 
 public void setCornerAngle(int cornerAngle) {
  this.mCornerAngle = cornerAngle;
 }
 
 // 绘制 损害框(直角矩形框)
 private void drawRect(Canvas canvas) {
 
  canvas.drawRect(mRectF, mPaint);
 
  // 绘制名称 和 概率
//  final String labelString =
//    !TextUtils.isEmpty(mTitle)
//      ? String.format("%s %.2f", mTitle, (100 * mConfidence))
//      : String.format("%.2f", (100 * mConfidence));
 
  // 在 直角矩形框 上写字
//  mBorderedText.drawText(canvas,
//    mRectF.left,
//    mRectF.top, labelString + "%",
//    mPaint);
 }
 
 // 绘制 损害框(圆角矩形框)
 private void drawRoundRect(Canvas canvas) {
  float cornerSize = Math.min(mRectF.width(), mRectF.height()) / 8.0f;
  canvas.drawRoundRect(mRectF, cornerSize, cornerSize, mPaint);
 
  // 绘制名称 和 概率
//  final String labelString =
//    !TextUtils.isEmpty(mTitle)
//      ? String.format("%s %.2f", mTitle, (100 * mConfidence))
//      : String.format("%.2f", (100 * mConfidence));
 
  // 在 圆角矩形框 上写字
//  mBorderedText.drawText(canvas,
//    mRectF.left + cornerSize,
//    mRectF.top, labelString + "%",
//    mPaint);
 }
 
 public void setLocationListener(onLocationListener mLocationListener) {
  this.mLocationListener = mLocationListener;
 }
 
 public interface onLocationListener {
  void locationRect(float startX, float startY, float endX, float endY);
 }
 
 
}

2.Activity里的应用

package com.xinrui.screenshot;

import android.app.Activity;
import android.graphics.RectF;
import android.os.Bundle;
import android.util.Log;
import android.widget.RelativeLayout;

import com.xinrui.screenshot.view.CropRectView;

public class MainActivity extends Activity {
 private RelativeLayout main_area;
 CropRectView cropRectView;
 @Override
 protected void onCreate(Bundle savedInstanceState) {
  super.onCreate(savedInstanceState);
  setContentView(R.layout.activity_main);
  initview();
 }

 private void initview(){
  main_area = (RelativeLayout)findViewById(R.id.main_area);
  cropRectView = (CropRectView)findViewById(R.id.main_img);
  RectF rectF = new RectF(660, 240, 1260, 840);
  cropRectView.setRectF(rectF);

  cropRectView.setLocationListener(new CropRectView.onLocationListener() {
   @Override
   public void locationRect(float startX, float startY, float endX, float endY) {
    Log.e("MainActivity","[ startX:(" + startX + ")--startY:(" + startY + ")--endX:(" + endX + ")--endY:(" + endY + ") ]");
   }
  });
 }
}

3.activity_main.xml

<?xml version="1.0" encoding="utf-8"?>

看完上述内容，是不是对Android自定义View实现可拖拽缩放的矩形框的方法有进一步的了解，如果还想学习更多内容，欢迎关注创新互联行业资讯频道。


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