Fatal编程技术网
  • java/
  • Java 画布（onDraw）Android

Java 画布（onDraw）Android

java android

Java 画布（onDraw）Android,java,android,android-canvas,ondraw,Java,Android,Android Canvas,Ondraw,我一直试图在画布上画不同的矩形后，多次点击按钮。它应该显示不同颜色的矩形，并且在每次单击按钮后矩形应该保持在画布上。矩形应该能够在画布上移动。我已经编写了View类，但我不知道如何在单击按钮后在activity上实现onDraw（）方法，也不知道如何创建不同颜色的矩形 我的main.xml文件上有4个按钮 public class DrawRectangle extends View { public DrawRectangle(Context context){ super(con

我一直试图在画布上画不同的矩形后，多次点击按钮。它应该显示不同颜色的矩形，并且在每次单击按钮后矩形应该保持在画布上。矩形应该能够在画布上移动。我已经编写了View类，但我不知道如何在单击按钮后在activity上实现onDraw（）方法，也不知道如何创建不同颜色的矩形

我的main.xml文件上有4个按钮

public class DrawRectangle extends View {

public DrawRectangle(Context context){

    super(context);

}

@Override
protected void onDraw(Canvas canvas) {
    // TODO Auto-generated method stub
    super.onDraw(canvas);

    Rect ourRect = new Rect();

    ourRect.set(0, 0, canvas.getWidth()/2, canvas.getHeight()/2);

    Paint blue = new Paint();

    blue.setColor(Color.BLUE);

    blue.setStyle(Paint.Style.FILL);

    //Draw to actual canvas
    canvas.drawRect(ourRect, blue);

}
}

这是我的活动课

public class MainActivity extends Activity {

Button bluebutton, redbutton, yellowbutton, greenbutton;
DrawRectangle dr;
Canvas canvas;

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.main);

    dr = new DrawRectangle(this);

    bluebutton = (Button)findViewById(R.id.bluebutton);
    redbutton = (Button)findViewById(R.id.redbutton);
    yellowbutton = (Button)findViewById(R.id.yellowbutton);
    greenbutton = (Button)findViewById(R.id.greenbutton);



bluebutton.setOnClickListener(new View.OnClickListener() {

    @Override
    public void onClick(View arg0) {
        // TODO Auto-generated method stub

                dr.onDraw();
    }
});
}
}

我是否也必须实现onTouchListener以便矩形可以四处移动

请给我一些建议。谢谢。

是的，您必须在视图子类中
onTouchEvent
。您可以阅读文档。事件参数包含有关您正在获得的触摸类型的信息（
ACTION\u DOWN
、
ACTION\u MOVE
、
ACTION\u UP
）以及触摸事件的坐标。
当您得到ACTION\u MOVE事件时，您可以更改矩形的位置并调用
invalidate（）
重新绘制。请摆脱活动中
onClickListener
中的draw调用

是的，您必须在视图子类中
onTouchEvent
。您可以阅读文档。事件参数包含有关您正在获得的触摸类型的信息（
ACTION\u DOWN
、
ACTION\u MOVE
、
ACTION\u UP
）以及触摸事件的坐标。
当您得到ACTION\u MOVE事件时，您可以更改矩形的位置并调用
invalidate（）
重新绘制。请在活动中的
onClickListener
中删除draw调用

您应该能够在onClick方法中为每个按钮使画布无效。添加一些布尔变量，告诉onDraw方法要绘制什么颜色

public static boolean isBlue, isRed, isYellow, isGreen;
public class MainActivity extends Activity {

    Button bluebutton, redbutton, yellowbutton, greenbutton;
    DrawRectangle dr;
    Canvas canvas;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.main);

    dr = new DrawRectangle(this);

    bluebutton = (Button)findViewById(R.id.bluebutton);
    redbutton = (Button)findViewById(R.id.redbutton);
    yellowbutton = (Button)findViewById(R.id.yellowbutton);
    greenbutton = (Button)findViewById(R.id.greenbutton);

    boolean blueColor = false;
    bluebutton.setOnClickListener(new View.OnClickListener() {

    @Override
    public void onClick(View arg0) {
        // TODO Auto-generated method stub
        isBlue = true;
        isRed = false;
        isGreen = false;
        isYellow = false;
        dr.invalidate();
    }
    });
}

//Used for storing rectangles        
public static List<Rect> rectangles;
public class DrawRectangle extends View {

    public DrawRectangle(Context context){

    super(context);

}

@Override
protected void onDraw(Canvas canvas) {
    super.onDraw(canvas);

    //Draw previous rectangles
    for(int i=0;i<rectangles.size();i++){
        canvas.drawRect(rectangles.get(i), paintColor );
    }
    Rect ourRect = new Rect();

    ourRect.set(0, 0, canvas.getWidth()/2, canvas.getHeight()/2);

    Paint paintColor = new Paint();

    if(MainActivity.isBlue){
        paintColor.setColor(Color.BLUE);
    }

    paintColor.setStyle(Paint.Style.FILL);

    //Draw to actual canvas
    canvas.drawRect(ourRect, paintColor );
    rectangles.add(ourRect)
更新onDraw方法以查看要绘制的颜色

public static boolean isBlue, isRed, isYellow, isGreen;
public class MainActivity extends Activity {

    Button bluebutton, redbutton, yellowbutton, greenbutton;
    DrawRectangle dr;
    Canvas canvas;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.main);

    dr = new DrawRectangle(this);

    bluebutton = (Button)findViewById(R.id.bluebutton);
    redbutton = (Button)findViewById(R.id.redbutton);
    yellowbutton = (Button)findViewById(R.id.yellowbutton);
    greenbutton = (Button)findViewById(R.id.greenbutton);

    boolean blueColor = false;
    bluebutton.setOnClickListener(new View.OnClickListener() {

    @Override
    public void onClick(View arg0) {
        // TODO Auto-generated method stub
        isBlue = true;
        isRed = false;
        isGreen = false;
        isYellow = false;
        dr.invalidate();
    }
    });
}

//Used for storing rectangles        
public static List<Rect> rectangles;
public class DrawRectangle extends View {

    public DrawRectangle(Context context){

    super(context);

}

@Override
protected void onDraw(Canvas canvas) {
    super.onDraw(canvas);

    //Draw previous rectangles
    for(int i=0;i<rectangles.size();i++){
        canvas.drawRect(rectangles.get(i), paintColor );
    }
    Rect ourRect = new Rect();

    ourRect.set(0, 0, canvas.getWidth()/2, canvas.getHeight()/2);

    Paint paintColor = new Paint();

    if(MainActivity.isBlue){
        paintColor.setColor(Color.BLUE);
    }

    paintColor.setStyle(Paint.Style.FILL);

    //Draw to actual canvas
    canvas.drawRect(ourRect, paintColor );
    rectangles.add(ourRect)

//用于存储矩形
公共静态列表矩形；
公共类DrawRectangle扩展视图{
公共绘图矩形（上下文）{
超级（上下文）；
}
@凌驾
受保护的void onDraw（画布）{
super.onDraw（帆布）；
//绘制前面的矩形

对于（int i=0；i您应该能够在onClick方法中为每个按钮使画布无效。添加一些布尔变量来告诉onDraw方法要绘制什么颜色


public static boolean isBlue, isRed, isYellow, isGreen;
public class MainActivity extends Activity {

    Button bluebutton, redbutton, yellowbutton, greenbutton;
    DrawRectangle dr;
    Canvas canvas;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.main);

    dr = new DrawRectangle(this);

    bluebutton = (Button)findViewById(R.id.bluebutton);
    redbutton = (Button)findViewById(R.id.redbutton);
    yellowbutton = (Button)findViewById(R.id.yellowbutton);
    greenbutton = (Button)findViewById(R.id.greenbutton);

    boolean blueColor = false;
    bluebutton.setOnClickListener(new View.OnClickListener() {

    @Override
    public void onClick(View arg0) {
        // TODO Auto-generated method stub
        isBlue = true;
        isRed = false;
        isGreen = false;
        isYellow = false;
        dr.invalidate();
    }
    });
}



//Used for storing rectangles        
public static List<Rect> rectangles;
public class DrawRectangle extends View {

    public DrawRectangle(Context context){

    super(context);

}

@Override
protected void onDraw(Canvas canvas) {
    super.onDraw(canvas);

    //Draw previous rectangles
    for(int i=0;i<rectangles.size();i++){
        canvas.drawRect(rectangles.get(i), paintColor );
    }
    Rect ourRect = new Rect();

    ourRect.set(0, 0, canvas.getWidth()/2, canvas.getHeight()/2);

    Paint paintColor = new Paint();

    if(MainActivity.isBlue){
        paintColor.setColor(Color.BLUE);
    }

    paintColor.setStyle(Paint.Style.FILL);

    //Draw to actual canvas
    canvas.drawRect(ourRect, paintColor );
    rectangles.add(ourRect)


更新onDraw方法以查看要绘制的颜色


public static boolean isBlue, isRed, isYellow, isGreen;
public class MainActivity extends Activity {

    Button bluebutton, redbutton, yellowbutton, greenbutton;
    DrawRectangle dr;
    Canvas canvas;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.main);

    dr = new DrawRectangle(this);

    bluebutton = (Button)findViewById(R.id.bluebutton);
    redbutton = (Button)findViewById(R.id.redbutton);
    yellowbutton = (Button)findViewById(R.id.yellowbutton);
    greenbutton = (Button)findViewById(R.id.greenbutton);

    boolean blueColor = false;
    bluebutton.setOnClickListener(new View.OnClickListener() {

    @Override
    public void onClick(View arg0) {
        // TODO Auto-generated method stub
        isBlue = true;
        isRed = false;
        isGreen = false;
        isYellow = false;
        dr.invalidate();
    }
    });
}



//Used for storing rectangles        
public static List<Rect> rectangles;
public class DrawRectangle extends View {

    public DrawRectangle(Context context){

    super(context);

}

@Override
protected void onDraw(Canvas canvas) {
    super.onDraw(canvas);

    //Draw previous rectangles
    for(int i=0;i<rectangles.size();i++){
        canvas.drawRect(rectangles.get(i), paintColor );
    }
    Rect ourRect = new Rect();

    ourRect.set(0, 0, canvas.getWidth()/2, canvas.getHeight()/2);

    Paint paintColor = new Paint();

    if(MainActivity.isBlue){
        paintColor.setColor(Color.BLUE);
    }

    paintColor.setStyle(Paint.Style.FILL);

    //Draw to actual canvas
    canvas.drawRect(ourRect, paintColor );
    rectangles.add(ourRect)



//用于存储矩形
公共静态列表矩形；
公共类DrawRectangle扩展视图{
公共绘图矩形（上下文）{
超级（上下文）；
}
@凌驾
受保护的void onDraw（画布）{
super.onDraw（帆布）；
//绘制前面的矩形

对于（int i=0；我感谢您的回复和建议。我已对代码进行了修改，但当单击按钮时，不会绘制矩形。问题，我是否必须在xml上指定表面视图？我已将setContentView（）设置为=setContentView（dr）；并绘制了矩形。但是4个按钮丢失了。我如何保留按钮和矩形？请提供main.xml文件好吗？我已经设法解决了。如果您不介意，可以详细说明用于存储先前绘制的矩形部分的向量吗？我可以使用List ListOfRect=new ArrayList（）；或矩形r=新矩形（）；要存储？我也可以使用此方法存储图像，对吗？此外，现在，当按钮单击时，矩形仅显示一次。我如何对其进行编码，以便即使按钮单击两次，也会显示两个矩形？感谢您的回复和建议。我已对代码进行了修改，但当按钮单击r时未绘制ectangle。问题，是否必须在xml上指定surfaceView？我已将setContentView（）设置为be=setContentView（dr）；并绘制了矩形。但是4个按钮丢失了。我如何保留按钮和矩形？请提供main.xml文件好吗？我已经设法解决了。如果您不介意，可以详细说明用于存储先前绘制的矩形部分的向量吗？我可以使用List ListOfRect=new ArrayList（）；或矩形r=new Rectangle（）；要存储？我也可以使用此方法存储图像，对吗？而且，现在，当按钮单击时，矩形仅显示一次。我如何对其进行编码，以便即使按钮单击两次，也会显示两个矩形？