xml中使用属性

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    xmlns:app="http://schemas.android.com/apk/res-auto" //自动查找
    xmlns:tools="http://schemas.android.com/tools"
    android:orientation="vertical">
    <CustomView 
        android:layout_width="match_parent"
        android:layout_height="60dp"
        app:line_color=""
    />
</RelativeLayout>

public class CustomView extends View {

    public DottedLineView(Context context, @Nullable AttributeSet attrs, int defStyleAttr) {
        super(context, attrs, defStyleAttr);
        // 根据Style拿到TypedArray
        TypedArray array = getContext().obtainStyledAttributes(attrs, R.styleable.ExEditText);
        mLineColor = array.getColor(R.styleable.ExEditText_line_color, getResources().getColor(R.color.Red));
        mLineStrokeHeight = array.getDimension(R.styleable.ExEditText_line_stroke_height, dp2px(getContext(), 1));
        array.recycle();
    }
}

setColor(int color)

paint.setColor(Color.parseColor("#009688"));
canvas.drawRect(30, 30, 230, 180, paint);


setARGB(int a, int r, int g, int b)

paint.setARGB(100, 255, 0, 0);
canvas.drawRect(0, 0, 200, 200, paint);

Activity.java

public void startActivityForResult(@RequiresPermission Intent intent, int requestCode,
        @Nullable Bundle options) {
    if (mParent == null) {
        options = transferSpringboardActivityOptions(options);
        Instrumentation.ActivityResult ar =
            mInstrumentation.execStartActivity(
                this, mMainThread.getApplicationThread(), mToken, this,
                intent, requestCode, options);
        if (ar != null) {
            mMainThread.sendActivityResult(
                mToken, mEmbeddedID, requestCode, ar.getResultCode(),
                ar.getResultData());
        }
        if (requestCode >= 0) {
            // If this start is requesting a result, we can avoid making
            // the activity visible until the result is received.  Setting
            // this code during onCreate(Bundle savedInstanceState) or onResume() will keep the
            // activity hidden during this time, to avoid flickering.
            // This can only be done when a result is requested because
            // that guarantees we will get information back when the
            // activity is finished, no matter what happens to it.
            mStartedActivity = true;
        }
    
        cancelInputsAndStartExitTransition(options);
        // TODO Consider clearing/flushing other event sources and events for child windows.
    } else {
        if (options != null) {
            mParent.startActivityFromChild(this, intent, requestCode, options);
        } else {
            // Note we want to go through this method for compatibility with
            // existing applications that may have overridden it.
            mParent.startActivityFromChild(this, intent, requestCode);
        }
    }
}