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這篇文章主要講解了Android自定義View實現可拖拽縮放的矩形框的方法，內容清晰明了，對此有興趣的小伙伴可以學習一下，相信大家閱讀完之后會有幫助。
在開發項目中，需要一個矩形框來實現截屏功能，并且還需要可以任意拖拽和縮放，這就需要自定義View來實現了，具體功能如下：
1.自定義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 {
// 繪制 損害框和損害名稱
private Paint mPaint;
private RectF mRectF;
// 邊緣字體
// private BorderedText mBorderedText;
// 標題 或 名字
private String mTitle;
// 概率
private float mConfidence;
// 矩形框 corner 的角度：直角、圓角
private int mCornerAngle;
//直角 默認
public static final int RIGHT_CORNER = 0;
//圓角
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();
//畫筆設置空心
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:// 繪制 損害框(直角矩形框)
// drawRect(canvas);
// break;
// case ROUND_CORNER:// 繪制 損害框(圓角矩形框)
// 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 上邊框-*/
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 |*/
// 繪制名稱 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 上寫字
// 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://拖動
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;
}
/*點擊頂點附近時的縮放處理*/
@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;
}
}
/*刷新矩形的坐標*/
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;
}
/*檢測矩形是否達到最小值*/
private boolean checkLegalRect(float cHeight, float cWidth) {
return (cHeight > minHeight && cWidth > minWidth);
}
/*從非法狀態恢復，這里處理的是達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;
}
}
/**
* 判斷點在矩形的什么位置
* @param cx
* @param cy
*/
private void checkMode(float cx, float cy) {
if (cx > startX && cx < endX && cy > startY && cy < endY) {
MODE = MODE_INSIDE;//矩形內部
} else if (nearbyPoint(cx, cy) < 4) {
MODE = MODE_POINT;//矩形點上
} else {
MODE = MODE_OUTSIDE;//矩形外部
}
}
/*矩形隨手指移動*/
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;
}
/*判斷點(inX,inY)是否靠近矩形的4個頂點*/
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;
}
// 設置矩形框
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;
}
// 繪制 損害框(直角矩形框)
private void drawRect(Canvas canvas) {
canvas.drawRect(mRectF, mPaint);
// 繪制名稱 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 上寫字
// mBorderedText.drawText(canvas,
// mRectF.left,
// mRectF.top, labelString + "%",
// mPaint);
}
// 繪制 損害框(圓角矩形框)
private void drawRoundRect(Canvas canvas) {
float cornerSize = Math.min(mRectF.width(), mRectF.height()) / 8.0f;
canvas.drawRoundRect(mRectF, cornerSize, cornerSize, mPaint);
// 繪制名稱 和 概率
// final String labelString =
// !TextUtils.isEmpty(mTitle)
// ? String.format("%s %.2f", mTitle, (100 * mConfidence))
// : String.format("%.2f", (100 * mConfidence));
// 在 圓角矩形框 上寫字
// 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里的應用
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"?> <RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android" android:id="@+id/main_area" android:layout_width="match_parent" android:layout_height="match_parent"> <com.xinrui.screenshot.view.CropRectView android:id="@+id/main_img" android:layout_centerInParent="true" android:layout_width="match_parent" android:layout_height="match_parent"/> </RelativeLayout>
看完上述內容，是不是對Android自定義View實現可拖拽縮放的矩形框的方法有進一步的了解，如果還想學習更多內容，歡迎關注億速云行業資訊頻道。
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