英文:
why doesn't onSizeChanged return View's correct dimensions?
问题
我正在构建一个自定义视图。将自定义视图插入xml时，我将其设置为单个子视图，并将其**layout_width**和**layout_height**设置为*match_parent*。
在**onSizeChanged**方法中打印其高度和宽度时，我得到的不是屏幕尺寸的宽度和高度，而只是我无法理解其计算方式的尺寸。
我正在三星Galaxy S8设备上运行该应用。
Xml：
<?xml version="1.0" encoding="utf-8"?>
<androidx.constraintlayout.widget.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
tools:context=".MainActivity">
<com.example.ptacticedrawimg.Rectangle
android:layout_width="match_parent"
android:layout_height="match_parent"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toTopOf="parent"/>
</androidx.constraintlayout.widget.ConstraintLayout>
自定义视图代码：
public class Rectangle extends View {
public Rectangle(Context context) {
super(context);
Log.e("Rectangle Constructor1","runs");
}
public Rectangle(Context context, AttributeSet attr)
{
super(context,attr);
Log.e("Rectangle Constructor2","runs");
}
public Rectangle(Context context, AttributeSet attrs, int defStyle) {
super(context, attrs, defStyle);
Log.e("Rectangle Constructor3","runs");
}
@Override
protected void onSizeChanged(int w, int h, int oldw, int oldh) {
super.onSizeChanged(w, h, oldw, oldh);
Log.e("onSizeChanged","oldh = " + oldh + " oldh = " +oldh + "h = " + h + " w = " + w);
}
@Override
protected void onDraw(Canvas canvas) {
Log.e("1234",""+ getMeasuredWidth());
super.onDraw(canvas);
LinearGradient linearGradient = new LinearGradient(200, 200, 600, 600, Color.GREEN, Color.YELLOW, Shader.TileMode.REPEAT);
Paint mPaint = new Paint();
mPaint.setShader(linearGradient);
canvas.drawRect(200, 200, 600, 600, mPaint);
}
日志输出：
2020-07-23 14:27:10.034 9633-9633/com.example.ptacticedrawimg E/Rectangle Constructor2: runs
2020-07-23 14:27:17.250 9633-9633/com.example.ptacticedrawimg E/onSizeChanged: oldh = 0 oldh = 0h = 1836 w = 1080
2020-07-23 14:27:17.295 9633-9633/com.example.ptacticedrawimg E/1234: 1080
英文:
I'm building a custom view. When inserting custom view to xml, i'm setting it as a single child and sets it's layout_width and layout_height to match_parent.
When printing its height and width in onSizeChange method, i don't get the width and height screen size, just dimensions that i can't understand how they where calculated.
I'm running the app on Samsung Galaxy S8 device.
Xml:
<?xml version="1.0" encoding="utf-8"?>
<androidx.constraintlayout.widget.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
tools:context=".MainActivity">
<com.example.ptacticedrawimg.Rectangle
android:layout_width= "match_parent"
android:layout_height="match_parent"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toTopOf="parent"/>
</androidx.constraintlayout.widget.ConstraintLayout>
Custom View Code:
public class Rectangle extends View {
public Rectangle(Context context) {
super(context);
Log.e("Rectangle Constructor1","runs");
}
public Rectangle(Context context, AttributeSet attr)
{
super(context,attr);
Log.e("Rectangle Constructor2","runs");
}
public Rectangle(Context context, AttributeSet attrs, int defStyle) {
super(context, attrs, defStyle);
Log.e("Rectangle Constructor3","runs");
}
@Override
protected void onSizeChanged(int w, int h, int oldw, int oldh) {
super.onSizeChanged(w, h, oldw, oldh);
Log.e("onSizeChanged","oldh = " + oldh + " oldh = " +oldh + "h = " + h + " w = " + w);
}
@Override
protected void onDraw(Canvas canvas) {
Log.e("1234",""+ getMeasuredWidth());
super.onDraw(canvas);
LinearGradient linearGradient = new LinearGradient(200, 200, 600, 600, Color.GREEN, Color.YELLOW, Shader.TileMode.REPEAT);
Paint mPaint = new Paint();
mPaint.setShader(linearGradient);
canvas.drawRect(200, 200, 600, 600, mPaint);
}
Log Output:
2020-07-23 14:27:10.034 9633-9633/com.example.ptacticedrawimg E/Rectangle Constructor2: runs
2020-07-23 14:27:17.250 9633-9633/com.example.ptacticedrawimg E/onSizeChanged: oldh = 0 oldh = 0h = 1836 w = 1080
2020-07-23 14:27:17.295 9633-9633/com.example.ptacticedrawimg E/1234: 1080
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