我编写了一个在Canvas上绘制的程序。
它提供了一个弹出菜单,其中包含3个绘图工具选项:
代码如下:
它提供了一个弹出菜单,其中包含3个绘图工具选项:
- 在屏幕上刮过时绘制直线
- 基于屏幕上的起点和终点绘制直线
- 绘制圆形
- 清除
- 撤消
List<Path>
)。但是问题就从这里开始了。圆形是使用Point对象绘制的。所以问题如下:
- 我无法让Android区分线和圆的绘制顺序。例如:我先画了5条线,然后画了5个圆,或者反过来。目前没有智能方式来遵循它们的绘制顺序。因此,撤消同时绘制线和圆的画布会导致混乱。
- 当前代码(尚未深入考虑)需要点击2次才能撤消圆形,而不是1次。
代码如下:
package com.example.orbit_.undofortouch;
import android.app.Activity;
import android.content.Context;
import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
import android.graphics.Canvas;
import android.graphics.Color;
import android.graphics.Paint;
import android.graphics.Path;
import android.graphics.Point;
import android.os.Bundle;
import android.util.AttributeSet;
import android.util.Log;
import android.view.MenuItem;
import android.view.MotionEvent;
import android.view.View;
import android.widget.Button;
import android.widget.LinearLayout;
import android.widget.PopupMenu;
import android.widget.Toast;
import java.util.ArrayList;
import java.util.List;
public class MainActivity extends Activity {
Button b1, b2, b3;
PopupMenu popup;
int dtool;
boolean touch,circle;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
LinearLayout linearLayout = (LinearLayout) findViewById(R.id.linearLayout2);
final DrawPanel dp = new DrawPanel(this);
linearLayout.addView(dp);
b1 = (Button) findViewById(R.id.button1);
b1.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
dp.Clear();
}
});
b2 = (Button) findViewById(R.id.button2);
b2.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
dp.Undo();
}
});
b3 = (Button) findViewById(R.id.button3);
b3.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
popup = new PopupMenu(MainActivity.this, v);
popup.getMenuInflater().inflate(R.menu.menu_main, popup.getMenu());
popup.setOnMenuItemClickListener(new PopupMenu.OnMenuItemClickListener() {
public boolean onMenuItemClick(MenuItem item) {
switch (item.getItemId()) {
case R.id.touch:
dtool = 1;
break;
case R.id.line:
dtool = 2;
break;
case R.id.circle:
dtool = 3;
break;
}
Log.v("EDITL:", "Drawtool:".concat(String.valueOf(item.getTitle())));
Toast.makeText(MainActivity.this,"Clicked popup menu item " + item.getTitle(),Toast.LENGTH_SHORT).show();
return true;
}
});
popup.show();
}
});
}
class DrawPanel extends View implements View.OnTouchListener {
Bitmap bmp;
Canvas canvas;
List<Path> paths, undone;
List<Point> circlePoints,removeCircles;
Paint paint;
Path path;
Point point;
public DrawPanel(Context context, AttributeSet attributeSet, int defStyle) {
super(context, attributeSet, defStyle);
}
public DrawPanel(Context context) {
super(context);
paint = new Paint();
path = new Path();
paths = new ArrayList<>();
undone = new ArrayList<>();
circlePoints = new ArrayList<>();
removeCircles = new ArrayList<>();
canvas = new Canvas();
this.setOnTouchListener(this);
paint.setStrokeWidth(3);
paint.setColor(Color.BLACK);
paint.setStyle(Paint.Style.STROKE);
paint.setDither(true);
paint.setAntiAlias(true);
paint.setStrokeCap(Paint.Cap.ROUND);
paint.setStrokeJoin(Paint.Join.ROUND);
bmp = BitmapFactory.decodeResource(getContext().getResources(), R.drawable.desert);
touch=false;
circle=false;
}
@Override
protected void onSizeChanged(int w, int h, int oldw, int oldh) {
super.onSizeChanged(w, h, oldw, oldh);
}
@Override
protected void onDraw(Canvas canvas) {
for (Path p : paths)
canvas.drawPath(p, paint);
if (touch)
canvas.drawPath(path, paint);
touch = false;
Log.v("Inside onDraw","Circle is".concat(String.valueOf(circle)));
for (Point p : circlePoints)
canvas.drawCircle(p.x, p.y, 5, paint);
}
float mX, mY,mx,my;
final float TOUCH_TOLERANCE = 0;
private void touch_start(float x, float y) {
undone.clear();
Log.v("ONTOUCH:", "Inside DOWN".concat("DOWN-X---:").concat(String.valueOf(x)).concat("**DOWN-Y---:").concat(String.valueOf(y)));
path.reset();
path.moveTo(x, y);
mX = x;
mY = y;
mx = x;
my = y;
}
private void touch_up() {
paths.add(path);
path = new Path();
}
private void touch_move(float x, float y) {
path.moveTo(mX, mY);
Log.v("ONTOUCH:", "Inside MOVE".concat("mX:").concat(String.valueOf(mX)).concat("mY:").concat(String.valueOf(mY)));
Log.v("ONTOUCH:", "Inside MOVE".concat("MOVE-X---:").concat(String.valueOf(x)).concat("**MOVE-Y---:").concat(String.valueOf(y)));
float dx = Math.abs(x - mX);
float dy = Math.abs(y - mY);
if (dx >= TOUCH_TOLERANCE || dy >= TOUCH_TOLERANCE) {
path.quadTo(mX, mY, (x + mX) / 2, (y + mY) / 2);
mX = x;
mY = y;
}
path.lineTo(mX, mY);
Log.v("MOVE:", " PATH ADDED & New Created");
}
@Override
public boolean onTouch(View v, MotionEvent event) {
float x = event.getX();
float y = event.getY();
switch (dtool) {
case 1:
touch=true;
Touch(v, event, x, y);
break;
case 2:
Line(v,event,x,y);
break;
case 3:
Circle(v,event,x,y);
break;
}
Log.v("ONTOUCH:", "OUTSIDE CASE");
return true;
}
public void Line(View v, MotionEvent event, float x, float y) {
switch (event.getAction()) {
case MotionEvent.ACTION_DOWN:
touch_start(x, y);
invalidate();
break;
case MotionEvent.ACTION_UP:
touch_up();
invalidate();
break;
case MotionEvent.ACTION_MOVE:
touch_move(x, y);
invalidate();
break;
}
}
public void Touch(View v, MotionEvent event, float x, float y) {
switch (event.getAction()) {
case MotionEvent.ACTION_DOWN:
touch_start(x, y);
invalidate();
canvas.drawPath(path, paint);
break;
case MotionEvent.ACTION_UP:
touch_up();
invalidate();
canvas.drawPath(path, paint);
break;
case MotionEvent.ACTION_MOVE:
touch_move(x, y);
invalidate();
break;
}
}
public void Circle(View v, MotionEvent event, float x, float y)
{ point = new Point();
point.x = (int)x;
point.y = (int)y;
path.moveTo(x,y);
circle=true;
if(event.getAction()==MotionEvent.ACTION_DOWN) {
circlePoints.add(new Point(Math.round(point.x), Math.round(point.y)));
invalidate();
Log.v("Circle", "Inside Circle");
circlePoints.add(point);
paths.add(path);
}
}
public void Clear() {
paths.clear(); //Needs to be experimented
path.reset();
invalidate();
}
public void Undo() {
if (paths.size() > 0) {
undone.add(paths.remove(paths.size() - 1));
invalidate();
}
else if(circlePoints.size()>0)
{
removeCircles.add(circlePoints.remove(circlePoints.size()-1));
invalidate();
}
}
}
}
XML布局代码:
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="fill_parent"
android:layout_height="fill_parent"
android:orientation="vertical" >
<LinearLayout
android:id="@+id/linearLayout2"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="vertical"
android:layout_weight="0"
android:layout_gravity="top">
</LinearLayout>
<Button
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="Undo"
android:id="@+id/button2"
android:layout_gravity="right"
android:layout_marginTop="-50dp" />
<Button
android:id="@+id/button1"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="Clear"
android:layout_gravity="center_vertical|bottom"
android:layout_marginTop="-50dp"
android:enabled="true" />
<Button
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="Tools"
android:id="@+id/button3"
android:layout_gravity="center_horizontal"
android:layout_weight="0"
android:layout_marginTop="-50dp" />
</LinearLayout>
XML主菜单代码:
<menu xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools" tools:context=".MainActivity">
<item
android:id="@+id/touch"
android:title="Touch"/>
<item
android:id="@+id/circle"
android:title="Circle"/>
<item
android:id="@+id/line"
android:title="Line"/>
</menu>
Path#addCircle(float x,float y,float radius,Path.Direction dir)
。 - pskink