android - 使用 new 关键字实例化 customview 对象时,不会调用 Android draw()
问题描述
我有一个带有相应自定义布局 xml 的自定义视图,我想在列表视图中显示它(因此我可以在列表中包含多个)。
作为一个测试,我在 onCreate() 中做了这个:
cstmView s = findViewById(R.id.card);
s.setImg(R.drawable.ac);
和:
<views.cstmView
android:layout_width="395dp"
android:layout_height="72dp"
android:layout_marginStart="8dp"
android:layout_marginTop="8dp"
android:layout_marginEnd="8dp"
android:layout_marginBottom="8dp"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toTopOf="parent" />
所以我知道视图正在被初始化和绘制cstmView.java
但是,我想创建一个列表视图,以便cstmView
在可滚动列表中有多个。这就是我所做的(作为测试,我只是在列表视图中放了一个 cstmView):
Listv = new ArrayList<>();
//adding just one cstmview
Listv.add(new cstmView(this.getApplicationContext()));
//this is my custom adapter to accept cstm layour rathern than a textview
cstmAdapter adapter = new cstmAdapter(this, R.layout.cstm_view, ListV);
ListView cstmListView = findViewById(R.id.cstmListView);
cstmListView(adapter);
尽管这会将 cstmView 放入列表中,但它并没有draw
在cstmView
.
我认为问题在于,new cstmView(this.getApplicationContext())
因为无论有没有列表视图都会出现同样的问题。new
关键字不运行吗draw()
?
这是应该在 cstmView.java 中调用 draw 的方法
public void init(Context context){
System.out.println("INIT");
// To instantiate an XML layout file from the already configured R.layout
LayoutInflater.from(context).inflate(R.layout.cstm_view, this);
// Get elements in layout
text = (TextView)findViewById(R.id.title);
back = (ImageView)findViewById(R.id.img);
DisplayMetrics metrics = context.getResources().getDisplayMetrics();
// to convert
cornerRadius = TypedValue.applyDimension(TypedValue.COMPLEX_UNIT_DIP, CORNER_RADIUS, metrics);
paint = new Paint(Paint.ANTI_ALIAS_FLAG);
maskPaint = new Paint(Paint.ANTI_ALIAS_FLAG | Paint.FILTER_BITMAP_FLAG);
maskPaint.setXfermode(new PorterDuffXfermode(PorterDuff.Mode.CLEAR));
// to draw the above
setWillNotDraw(false);
}
然后 on draw 函数创建一些位图等等......
@Override
public void draw(Canvas canvas) {
System.out.println("DRAW");
// create a bitmap with this context height and width
Bitmap offscreenBitmap = Bitmap.createBitmap(getWidth(), getHeight(), Bitmap.Config.ARGB_8888);
Canvas offscreenCanvas = new Canvas(offscreenBitmap);
super.draw(offscreenCanvas);
if (maskBitmap == null) {
maskBitmap = createMask(getWidth(), getHeight());
}
offscreenCanvas.drawBitmap(maskBitmap, 0f, 0f, maskPaint);
canvas.drawBitmap(offscreenBitmap, 0f, 0f, paint);
}
private Bitmap createMask(int width, int height) {
System.out.println("CREATE MASK");
Bitmap mask = Bitmap.createBitmap(width, height, Bitmap.Config.ALPHA_8);
Canvas canvas = new Canvas(mask);
Paint paint = new Paint(Paint.ANTI_ALIAS_FLAG);
paint.setColor(Color.WHITE);
canvas.drawRect(0, 0, width, height, paint);
paint.setXfermode(new PorterDuffXfermode(PorterDuff.Mode.CLEAR));
canvas.drawRoundRect(new RectF(0, 0, width, height), cornerRadius, cornerRadius, paint);
return mask;
}
更新
调用invalidate()
构造函数解决了这个问题。但是,我仍然没有看到draw
应该在屏幕上进行的渲染。有什么问题arrayAdatper
吗?:
@Override
public View getView(int position, View convertView, ViewGroup parent){
View rowView = convertView;
//if data already exists in list reuse the data rather than re inflate from scratch
if(rowView == null) {
LayoutInflater inflater;
inflater = LayoutInflater.from(context);
rowView = inflater.inflate(resource, parent, false);
}
return rowView;
}
解决方案
调用方法invalidate()
,它将隐式调用onDraw()
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