自定義組件基礎

自定義組件基礎

本案例主要簡述如何通過view繪製文字、圖形和圖片。

public class MyView2 extends View {

    private Bitmap bitmap;

    //自定義組件在佈局中調用時執行以下方法
    public MyView2(Context context, AttributeSet attrs) {
        super(context, attrs);
        bitmap = BitmapFactory.decodeResource(getResources(), R.drawable.ic_launcher);
    }

    //自定義組件在代碼中調用時執行以下方法
    public MyView2(Context context) {
        super(context);
        bitmap = BitmapFactory.decodeResource(getResources(), R.drawable.ic_launcher);
    }

    /**
     * 各條邊距離左上右下的距離（left,top,right,bottom）
     */
    @Override
    protected void onDraw(Canvas canvas) {
        super.onDraw(canvas);
        Paint paint = new Paint();
        paint.setAntiAlias(true);//抗鋸齒
        paint.setTextSize(30);
        canvas.drawText("my is onDraw", 0, 30, paint);

        canvas.drawLine(0, 50, 600, 50, paint);//畫直線
        canvas.drawRect(0, 90, 100, 190, paint);//畫矩形

        paint.setColor(Color.BLUE);//普通方法設置顏色
        //paint.setStyle(android.graphics.Paint.Style.STROKE);//空心矩形
        Rect r = new Rect(220, 150, 300, 240);
        canvas.drawRect(r, paint);//畫矩形

        RectF rectf = new RectF(0, 250, 100, 340);
        canvas.drawRoundRect(rectf, 11, 11, paint);//畫圓角矩形

        //paint.setColor(0xffffffff);//十六進制設置顏色
        canvas.drawCircle(400, 300, 50, paint);//畫圓形

        canvas.drawBitmap(bitmap, 100, 400, paint);//畫圖片
    }
}

activity_main.xml
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context=".MainActivity" >

    <com.trkj.dept12_customer1.MyView2
        android:background="#FF0000"
        android:layout_width="400dp"
        android:layout_height="match_parent" />

</RelativeLayout>

Activity:
public class MainActivity extends Activity {

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        //setContentView(R.layout.activity_main);//調用佈局
        setContentView(new MyView2(this));//調用自定義代碼

    }
}

各邊距示意圖：