Question

我想在白色画布上绘制红色圆圈，但它是黑色的，只有在第一次触摸后变成白色，所以我希望它在开始时是白色的。这是我的代码。（我也想知道浮动按钮出现的原因：D）

DrawingView.java：

class DrawingView extends SurfaceView {

private final Paint paint = new Paint(Paint.ANTI_ALIAS_FLAG);
private final SurfaceHolder surfaceHolder;
private ArrayList<Point> points;

public DrawingView(Context context, AttributeSet attrs) {
    super(context, attrs);
    paint.setColor(Color.RED);
    surfaceHolder = getHolder();
    paint.setStyle(Paint.Style.FILL);
    setFocusable(true);
    setFocusableInTouchMode(true);
    points = new ArrayList<>();
}

@Override
public boolean onTouchEvent(MotionEvent event) {
    points.add(new Point((int) event.getX(), (int) event.getY()));
    Canvas canvas = surfaceHolder.lockCanvas();
    canvas.drawColor(Color.WHITE);
    for (Point p : points)
        canvas.drawCircle(p.x, p.y, 50, paint);
    surfaceHolder.unlockCanvasAndPost(canvas);
    return false;
}

}

MainActivity.java：

public class MainActivity extends AppCompatActivity {

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

@Override
public boolean onCreateOptionsMenu(Menu menu) {
    menu.add(0, 0, 0, "Save")
            .setIcon(R.drawable.ic_save)
            .setOnMenuItemClickListener(new MenuItem.OnMenuItemClickListener() {
                @Override
                public boolean onMenuItemClick(MenuItem item) {
                    // do some magic to save :D
                    return false;
                }
            })
            .setShowAsAction(
                    MenuItem.SHOW_AS_ACTION_ALWAYS
                            | MenuItem.SHOW_AS_ACTION_WITH_TEXT);
    return super.onCreateOptionsMenu(menu);
}

}

activity_main.xml中

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
xmlns:app="http://schemas.android.com/apk/res-auto"
xmlns:fab="http://schemas.android.com/apk/res-auto"
android:layout_width="match_parent"
android:layout_height="match_parent"
tools:context=".MainActivity">

<com.github.clans.fab.FloatingActionMenu
    android:id="@+id/fab"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:layout_marginRight="10dp"
    android:layout_marginLeft="10dp"
    fab:menu_fab_size="normal"
    fab:menu_showShadow="true"
    fab:menu_shadowColor="#66000000"
    fab:menu_shadowRadius="4dp"
    fab:menu_shadowXOffset="1dp"
    fab:menu_shadowYOffset="3dp"
    fab:menu_colorNormal="#DA4336"
    fab:menu_colorPressed="#E75043"
    fab:menu_colorRipple="#99FFFFFF"
    fab:menu_animationDelayPerItem="50"
    fab:menu_icon="@drawable/fab_add"
    fab:menu_buttonSpacing="0dp"
    fab:menu_labels_margin="0dp"
    fab:menu_labels_showAnimation="@anim/fab_slide_in_from_right"
    fab:menu_labels_hideAnimation="@anim/fab_slide_out_to_right"
    fab:menu_labels_paddingTop="4dp"
    fab:menu_labels_paddingRight="8dp"
    fab:menu_labels_paddingBottom="4dp"
    fab:menu_labels_paddingLeft="8dp"
    fab:menu_labels_padding="8dp"
    fab:menu_labels_textColor="#FFFFFF"
    fab:menu_labels_textSize="14sp"
    fab:menu_labels_cornerRadius="3dp"
    fab:menu_labels_colorNormal="#333333"
    fab:menu_labels_colorPressed="#444444"
    fab:menu_labels_colorRipple="#66FFFFFF"
    fab:menu_labels_showShadow="true"
    fab:menu_labels_singleLine="false"
    fab:menu_labels_ellipsize="none"
    fab:menu_labels_maxLines="-1"
    fab:menu_labels_position="left"
    fab:menu_openDirection="up"
    fab:menu_backgroundColor="@android:color/transparent"
    android:layout_alignParentBottom="true"
    android:layout_alignParentEnd="true">

    <com.github.clans.fab.FloatingActionButton
        android:id="@+id/insertPhoto"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:src="@drawable/ic_insert_photo_24dp"
        fab:fab_size="mini"
        fab:fab_label="Add photos" />

    <com.github.clans.fab.FloatingActionButton
        android:id="@+id/addCircle"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:src="@drawable/ic_brightness_1_24dp"
        fab:fab_size="mini"
        fab:fab_label="Add circles" />

</com.github.clans.fab.FloatingActionMenu>

<reminder.com.paint.DrawingView
    android:layout_width="match_parent"
    android:layout_height="match_parent" />

Answer 1

我认为解决方法是在创建时使用，并在DrawingView.java中将颜色初始化为白色

public onCreate(...)
{
...

Set Color to white
...
}

继承人编辑： 真正的解决方案：在构造函数中使用setBackground函数并将其设置为白色

ClassName(...)
{
Setbackground("WHITE")
}

Android在画布上开始绘制白色

1 个答案: