android通过手指触摸屏幕上删除线

Question

我有一个自定义视图，其功能就像帆布。我可以在画布上绘制直线。我按路径绘制线条。我想要做的是通过触摸线删除随机线。任何人都可以帮助我？这就像当我们长时间点击我们的手机屏幕时，所有应用程序都震惊了，我可以选择一个删除它。 另一个问题是这个自定义视图中的对话框显示，我需要点击四次然后对话就可以解雇了。任何人都知道为什么？对不起我的英文很差，如果你不明白我的问题，任何问题都会让我知道。谢谢。

package com.icst.symmetry.View;

import android.app.AlertDialog;
import android.content.Context;
import android.content.DialogInterface;
import android.graphics.Canvas;
import android.graphics.Color;
import android.graphics.Paint;
import android.graphics.Path;
import android.util.AttributeSet;
import android.view.MotionEvent;
import android.view.View;

import com.icst.symmetry.Bean.Axis;
import com.icst.symmetry.Bean.Image;
import com.icst.symmetry.Bean.Line;
import com.icst.symmetry.R;
import com.icst.symmetry.Tools.Util;

import java.util.ArrayList;

/**
 * Created by hugo on 16/8/31.
 */
public class PaintView extends View {
    private static final String TAG = PaintView.class.getSimpleName();


    private Paint machinePaint;
    private Paint userPaint;
    private Line mLine;
    private Axis mAxis;
    private Path mPath;

    private ArrayList<Line> machineLines;
    private ArrayList<Line> saveLines;
    private ArrayList<Line> deleteLines;
    private boolean isEraseModel;
    AlertDialog mDialog;

    public PaintView(Context context) {
        super(context);
        init(context);
    }

    public PaintView(Context context, AttributeSet attrs) {
        super(context, attrs);
        init(context);
    }

    private void init(Context context) {
        saveLines = new ArrayList<>();
        deleteLines = new ArrayList<>();
        machineLines = new ArrayList<>();
        machinePaint = new Paint(Paint.ANTI_ALIAS_FLAG);
        userPaint = new Paint(Paint.ANTI_ALIAS_FLAG);
        mLine = new Line();
        mAxis = new Axis();
        mPath = new Path();
        machinePaint.setStyle(Paint.Style.STROKE);
        machinePaint.setStrokeWidth(4);
        machinePaint.setColor(Color.RED);
        userPaint.setStyle(Paint.Style.STROKE);
        userPaint.setStrokeWidth(4);
        userPaint.setColor(Color.BLACK);
    }

    @Override
    protected void onDraw(Canvas canvas) {
        if(machineLines.size()!=0){
            for(Line line :machineLines)
                canvas.drawPath(line.getPath(), machinePaint);
        }
        for (Line p : saveLines) {
            canvas.drawPath(p.getPath(), userPaint);
        }
        canvas.drawPath(mPath, userPaint);
    }


    @Override
    public boolean onTouchEvent(MotionEvent event) {
        float x = event.getX();
        float y = event.getY();
        if (!isEraseModel) {
            switch (event.getAction()) {
                case MotionEvent.ACTION_DOWN:
                    touch_start(x, y);
                    break;
                case MotionEvent.ACTION_MOVE:
                    touch_move(x, y);
                    invalidate();
                    break;
                case MotionEvent.ACTION_UP:
                    touch_up(x, y);
                    invalidate();
                    break;
            }
        } else {
            for (Line line : saveLines){
                if(Util.isTouched(line,x,y)){
                    showDialog(line);
                    break;
                }
            }

        }

        return true;
    }

    private void showDialog(Line line) {
        final Line mLine=line;
        AlertDialog.Builder builder =new AlertDialog.Builder(getContext());
        builder.setCancelable(true);
        builder.setPositiveButton(R.string.ok, new DialogInterface.OnClickListener() {
            @Override
            public void onClick(DialogInterface dialog, int which) {
                saveLines.remove(mLine);
                deleteLines.add(mLine);
                invalidate();
            }
        });
        builder.setNegativeButton(R.string.cancel, new DialogInterface.OnClickListener() {
            @Override
            public void onClick(DialogInterface dialog, int which) {
                dialog.dismiss();
            }
        });
        builder.setTitle("是否确认删除这条线？");
        mDialog = builder.create();
        mDialog.show();
    }

    private void touch_start(float x, float y) {
        mPath.reset();
        mPath.moveTo(x, y);
        mAxis.setxStart(x);
        mAxis.setyStart(y);
    }

    private void touch_move(float x, float y) {
        mPath.rewind();
        mPath.moveTo(x, y);
        mPath.lineTo(mAxis.getxStart(), mAxis.getyStart());
    }

    private void touch_up(float x, float y) {
        mAxis.setxEnd(x);
        mAxis.setyEnd(y);
        mLine.setAxis(mAxis);
        mLine.setPath(mPath);
        saveLines.add(mLine);
        mPath = new Path();
        mAxis = new Axis();
        mLine = new Line();
    }


    public void onClickEraser() {
        isEraseModel = true;
    }

    public void onClickDraw() {
        isEraseModel = false;
    }

    public void drawMachineLine(float[] data,Image image){
        machineLines.clear();
        float left=data[0];
        float top=data[1];
        float scaleX=data[2];
        float scaleY=data[3];
        for(int i=0;i<image.getMachineAxis().size();i++){
            Axis axis=image.getMachineAxis().get(i);
            axis.setxStart(axis.getxStart());
            Line line =new Line();
            line.setAxis(axis);
            Path path=new Path();
            path.moveTo(axis.getxEnd()*scaleX+left,axis.getyEnd()*scaleY+top);
            path.lineTo(axis.getxStart()*scaleX+left,axis.getyStart()*scaleY+top);
            line.setPath(path);
            machineLines.add(line);
        }
        invalidate();

    }
    public void undo() {
        if (saveLines != null && saveLines.size() > 0) {
            Line line = saveLines.get(saveLines.size() - 1);
            deleteLines.add(line);
            saveLines.remove(saveLines.size() - 1);
            invalidate();
        }
    }

    public void redo() {
        if (deleteLines != null && deleteLines.size() > 0) {
            Line line = deleteLines.get(deleteLines.size() - 1);
            saveLines.add(line);
            deleteLines.remove(deleteLines.size() - 1);
            invalidate();
        }
    }

}

Answer 1

好。 当您触摸屏幕并删除手指事件时：

ACTION_DOWN - 第一次触摸时

ACTION_MOVE - 当你在屏幕上移动手指时

ACTION_UP - 当你从屏幕上移开手指时

祝好运！