Java 拖动图像视图和图形-Android Studio 4.0
我正在尝试制作一个应用程序,当我在屏幕上拖动ImageView时,它需要画一条线。我试图在LinearLayouts下创建画布,但在拖动对象时,画布无法绘制。请帮帮我!下面是MainActivity、CanvasView类和xml文件中的代码。我不知道如何从CanvasView类调用onTouchEvent方法。当我触摸图标时,它会产生一个阴影,但不会画出超出我预期的线条Java 拖动图像视图和图形-Android Studio 4.0,java,android,drag-and-drop,drawing,paint,Java,Android,Drag And Drop,Drawing,Paint,我正在尝试制作一个应用程序,当我在屏幕上拖动ImageView时,它需要画一条线。我试图在LinearLayouts下创建画布,但在拖动对象时,画布无法绘制。请帮帮我!下面是MainActivity、CanvasView类和xml文件中的代码。我不知道如何从CanvasView类调用onTouchEvent方法。当我触摸图标时,它会产生一个阴影,但不会画出超出我预期的线条 package com.example.drawview; import androidx.appcompat.app.A
package com.example.drawview;
import androidx.appcompat.app.AppCompatActivity;
import androidx.constraintlayout.widget.ConstraintLayout;
import android.content.ClipData;
import android.content.Context;
import android.os.Bundle;
import android.view.MotionEvent;
import android.view.View;
public class MainActivity extends AppCompatActivity {
private CanvasView canvasView;
private ConstraintLayout mainLayout;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
findViewById(R.id.imageView).setOnTouchListener(new TouchEventView(this));
mainLayout = findViewById(R.id.screen);
canvasView = (CanvasView) findViewById(R.id.canvas);
}
public class TouchEventView extends View implements View.OnTouchListener {
public TouchEventView(Context context) {
super(context);
}
@Override
public boolean onTouch(View ve, MotionEvent event) {
canvasView.onTouchEvent(event);
ClipData data = ClipData.newPlainText("simple_text", "text");
View.DragShadowBuilder sb = new View.DragShadowBuilder(ve);
ve.startDrag(data, sb, ve, 0);
return true;
}
}
}
package com.example.drawview;
import android.content.ClipData;
import android.content.Context;
import android.graphics.Bitmap;
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 androidx.annotation.Nullable;
public class CanvasView extends View {
public int height;
public int width;
private Bitmap mBitmap;
private Canvas mCanvas;
private Path mPath;
private Paint mPaint;
private float mX, mY;
private final float TOLERANCE = 5;
Context context;
public CanvasView(Context context, @Nullable AttributeSet attrs) {
super(context, attrs);
this.context = context;
mPath = new Path();
mPaint = new Paint();
mPaint.setAntiAlias(true);
mPaint.setColor(Color.GREEN);
mPaint.setStyle(Paint.Style.STROKE);
mPaint.setStrokeJoin(Paint.Join.ROUND);
mPaint.setStrokeWidth(4f);
}
/*
public CanvasView(Context context) {
super(context);
this.context = context;
mPath = new Path();
mPaint = new Paint();
mPaint.setAntiAlias(true);
mPaint.setColor(Color.GREEN);
mPaint.setStyle(Paint.Style.STROKE);
mPaint.setStrokeJoin(Paint.Join.ROUND);
mPaint.setStrokeWidth(4f);
}
*/
@Override
protected void onSizeChanged(int w, int h, int oldw, int oldh) {
super.onSizeChanged(w, h, oldw, oldh);
mBitmap = Bitmap.createBitmap(w, h, Bitmap.Config.ARGB_8888);
mCanvas = new Canvas(mBitmap);
}
@Override
protected void onDraw(Canvas canvas) {
super.onDraw(canvas);
canvas.drawPath(mPath, mPaint);
}
private void startTouch(float x, float y){
mPath.moveTo(x, y);
mX = x;
mY = y;
}
private void moveTouch(float x, float y){
float dx = Math.abs(x - mX);
float dy = Math.abs(y - mY);
if(dx >= TOLERANCE || dy >= TOLERANCE){
mPath.quadTo(mX, mY,(x + mX)/2, (y + mY)/2);
mX = x;
mY = y;
}
}
public void clearCanvas(){
mPath.reset();
invalidate();
}
private void upTouch(){
mPath.lineTo(mX, mY);
}
public boolean onTouchEvent(MotionEvent event) {
float xPos = event.getX();
float yPos = event.getY();
switch (event.getAction()){
case MotionEvent.ACTION_DOWN:
startTouch(xPos, yPos);
invalidate();
break;
case MotionEvent.ACTION_MOVE:
moveTouch(xPos, yPos);
invalidate();
break;
case MotionEvent.ACTION_UP:
upTouch();
invalidate();
break;
}
return true;
}
}
<?xml version="1.0" encoding="utf-8"?>
<androidx.constraintlayout.widget.ConstraintLayout 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:id="@+id/screen"
android:layout_width="match_parent"
android:layout_height="match_parent"
tools:context=".MainActivity">
<com.example.drawview.CanvasView
android:id="@+id/canvas"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:layout_alignParentTop="true"
android:layout_centerHorizontal="true"
android:visibility="visible"
app:layout_constraintBottom_toBottomOf="parent"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintHorizontal_bias="0.0"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toTopOf="parent"
app:layout_constraintVertical_bias="0.0" />
<ImageView
android:id="@+id/imageView"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:contentDescription="@string/todo"
app:layout_constraintBottom_toBottomOf="parent"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toTopOf="parent"
app:srcCompat="@drawable/ic_launcher_foreground" />
</androidx.constraintlayout.widget.ConstraintLayout>
package com.example.drawview;
导入androidx.appcompat.app.appcompat活动;
导入androidx.constraintlayout.widget.constraintlayout;
导入android.content.ClipData;
导入android.content.Context;
导入android.os.Bundle;
导入android.view.MotionEvent;
导入android.view.view;
公共类MainActivity扩展了AppCompatActivity{
私人画布视图画布视图;
私有约束主布局;
@凌驾
创建时受保护的void(Bundle savedInstanceState){
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
findviewbyd(R.id.imageView).setOnTouchListener(新的TouchEventView(this));
mainLayout=findViewById(R.id.screen);
canvasView=(canvasView)findviewbyd(R.id.canvas);
}
公共类TouchEventView扩展视图实现View.OnTouchListener{
公共TouchEventView(上下文){
超级(上下文);
}
@凌驾
公共布尔onTouch(视图ve、运动事件){
canvasView.onTouchEvent(事件);
ClipData data=ClipData.newPlainText(“简单文本”、“文本”);
View.DragShadowBuilder sb=新视图.DragShadowBuilder(ve);
ve.startDrag(数据,sb,ve,0);
返回true;
}
}
}
包com.example.drawview;
导入android.content.ClipData;
导入android.content.Context;
导入android.graphics.Bitmap;
导入android.graphics.Canvas;
导入android.graphics.Color;
导入android.graphics.Paint;
导入android.graphics.Path;
导入android.util.AttributeSet;
导入android.view.MotionEvent;
导入android.view.view;
导入androidx.annotation.Nullable;
公共类画布视图扩展视图{
公众内部高度;
公共整数宽度;
私有位图mBitmap;
私人帆布mCanvas;
专用路径mPath;
私人油漆;
私人浮动mX,我的;
专用最终浮动公差=5;
语境;
公共画布视图(上下文上下文,@Nullable AttributeSet attrs){
超级(上下文,attrs);
this.context=上下文;
mPath=新路径();
mPaint=新油漆();
mPaint.setAntiAlias(true);
mPaint.setColor(Color.GREEN);
mPaint.setStyle(油漆、样式、笔划);
mPaint.setStrokeJoin(油漆.连接.圆形);
mPaint.设定行程宽度(4f);
}
/*
公共画布视图(上下文){
超级(上下文);
this.context=上下文;
mPath=新路径();
mPaint=新油漆();
mPaint.setAntiAlias(true);
mPaint.setColor(Color.GREEN);
mPaint.setStyle(油漆、样式、笔划);
mPaint.setStrokeJoin(油漆.连接.圆形);
mPaint.设定行程宽度(4f);
}
*/
@凌驾
已更改尺寸的受保护空心(整数w、整数h、整数oldw、整数oldh){
super.onSizeChanged(w,h,oldw,oldh);
mBitmap=Bitmap.createBitmap(w,h,Bitmap.Config.ARGB_8888);
mCanvas=新画布(mBitmap);
}
@凌驾
受保护的void onDraw(画布){
super.onDraw(帆布);
画布绘制路径(mPath,mPaint);
}
私有无效开始接触(浮动x、浮动y){
移动到(x,y)的速度;
mX=x;
mY=y;
}
私有void moveTouch(浮动x、浮动y){
float dx=Math.abs(x-mX);
float dy=Math.abs(y-mY);
如果(dx>=公差| | dy>=公差){
兆帕四分之一秒(mX,mY,(x+mX)/2,(y+mY)/2);
mX=x;
mY=y;
}
}
公共无效clearCanvas(){
mPath.reset();
使无效();
}
私有无效upTouch(){
mPath.lineTo(mX,mY);
}
公共布尔onTouchEvent(运动事件){
float xPos=event.getX();
float yPos=event.getY();
开关(event.getAction()){
case MotionEvent.ACTION\u DOWN:
startTouch(XPO、YPO);
使无效();
打破
case MotionEvent.ACTION\u移动:
moveTouch(XPO、YPO);
使无效();
打破
case MotionEvent.ACTION\u UP:
upTouch();
使无效();
打破
}
返回true;
}
}
xml文件在项目文件夹中不幸的是,您没有给我们任何线索,告诉我们您要达到的目的是什么。它是垂直的吗?它是水平的吗?从哪里开始?在哪里结束?我想画一条自由线,就像用铅笔在屏幕上画一样。我的应用程序会这样做,但当我拖动iImage时,它不会绘制任何内容。我发布了一个带有我的应用程序截图的链接。我很确定这是因为在拖动时不会调用onTouch()
方法。尝试将日志信息放在那里。