java在右侧绘制矩形

Question

下面是从左侧0像素处绘制矩形的代码，但是如何设置从屏幕右侧0像素处绘制矩形

    paint.setColor(Color.RED);
    canvas.drawRect(0, 0, 5, canvas.getHeight(), paint );

主要活动。xml

<LinearLayout
    xmlns:安卓="http://schemas.安卓.com/apk/res/安卓"
    xmlns:tools="http://schemas.安卓.com/tools"
    安卓:orientation="vertical"
    安卓:layout_width="fill_parent"
    安卓:layout_height="fill_parent"
    安卓:paddingLeft="@dimen/activity_horizontal_margin"
    安卓:paddingRight="@dimen/activity_horizontal_margin"
    安卓:paddingTop="@dimen/activity_vertical_margin"
    安卓:paddingBottom="@dimen/activity_vertical_margin"
    tools:context=".MainActivity">

    <TextView 安卓:text="@string/hello_world" 安卓:layout_width="wrap_content"
        安卓:layout_height="wrap_content" />

    <package.name.customview.Diagram
        安卓:id="@+id/diagram"
        安卓:layout_width="fill_parent"
        安卓:layout_height="52dp" />

</LinearLayout>

图表。java

package com.apptacularapps.customview;

import 安卓.content.Context;
import 安卓.graphics.Canvas;
import 安卓.graphics.Color;
import 安卓.graphics.Paint;
import 安卓.view.View;

public class Diagram extends View {
    Paint paint = new Paint();

    public Diagram(Context context) {
        super(context);
    }

    @Override
    public void onDraw(Canvas canvas) {
        paint.setColor(Color.RED);
        canvas.drawRect(0, 0, 5, canvas.getHeight(), paint );

        paint.setColor(Color.RED);
        canvas.drawRect(canvas.getWidth() - 5, 0, 5, canvas.getHeight(), paint );
    }
}

Answer 1

创建一个新类-DrawView。爪哇

    import android.content.Context;
    import android.graphics.Canvas;
    import android.graphics.Color;
    import android.graphics.Paint;
    import android.view.View;

    public class DrawView extends View {
        Paint paint = new Paint();

        public DrawView(Context context) {
            super(context);            
        }

        @Override
        public void onDraw(Canvas canvas) {

    //Code to Measure the Screen width in pixels

    Display display = getWindowManager().getDefaultDisplay();
    Point size = new Point();
    display.getSize(size);
    int width = size.x;

            paint.setColor(Color.RED);
    canvas.drawRect(0, 0, 5, canvas.getHeight(), paint );

    paint.setColor(Color.RED);
    canvas.drawRect(width-canvas.getWidth(), 0, width, canvas.getHeight(), paint );
        }
}

在你的图表中。java，如下更改onDraw方法

@Override
    public void onDraw(Canvas canvas) {
        DrawView drawView = new DrawView(this);
        drawView.setBackgroundColor(Color.WHITE);
        setContentView(drawView);
    }

更新-要解决错误，请尝试此操作

如果您不在活动中，您可以通过WINDOW_服务获得默认显示：

WindowManager wm = (WindowManager) context.getSystemService(Context.WINDOW_SERVICE);
Display display = wm.getDefaultDisplay();

而不是

Display display = getWindowManager().getDefaultDisplay();

更新2-解决上下文错误

将此行Context context;添加到此行Paint paint = new Paint();下方

将此行this.context = context;添加到此行super(context);下方

更新3-使用此代码示例

图表。爪哇

包com。案例研究。意图和过滤器； 导入android。应用程序。活动 导入android。图样颜色 导入android。操作系统。束

public class Diagram extends Activity {
    DrawView drawView;

    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);

        drawView = new DrawView(this);
        drawView.setBackgroundColor(Color.WHITE);
        setContentView(drawView);

    }
}

DrawView。爪哇

package com.casestudy.intentsandfilter;

import android.content.Context;
import android.graphics.Canvas;
import android.graphics.Color;
import android.graphics.Paint;
import android.view.View;

public class DrawView extends View {
    Paint paint = new Paint();

    public DrawView(Context context) {
        super(context);            
    }

    @Override
    public void onDraw(Canvas canvas) {
        paint.setColor(Color.BLACK);
        paint.setStrokeWidth(3);
        canvas.drawRect(30, 30, 80, 80, paint);
        paint.setStrokeWidth(0);
        paint.setColor(Color.CYAN);
        canvas.drawRect(33, 60, 77, 77, paint );
        paint.setColor(Color.YELLOW);
        canvas.drawRect(33, 33, 77, 60, paint );

    }

}