在画布上绘制文本并使其在屏幕上可见
这段代码应该将文本转换为图像
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
Paint paint = new Paint();
paint.setStyle(Paint.Style.FILL);
paint.setColor(Color.RED);
paint.setTextSize(16);
paint.setAntiAlias(true);
paint.setTypeface(Typeface.MONOSPACE);
Bitmap bm = Bitmap.createBitmap(16, 16, Bitmap.Config.ALPHA_8);
float x = bm.getWidth();
float y = bm.getHeight();
Canvas c = new Canvas(bm);
c.drawText("Test", x, y, paint);
}
这段代码可以吗？如果是，我怎样才能使这个新的位图在屏幕上可见？我尝试了这段代码，它产生了一个错误
setContentView(c); //<- ERROR!
，我对元素 Canvas 感到困惑，因为 XML 中没有这样的元素，我可以在代码中使用。
This code was supposed to convert text to image
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
Paint paint = new Paint();
paint.setStyle(Paint.Style.FILL);
paint.setColor(Color.RED);
paint.setTextSize(16);
paint.setAntiAlias(true);
paint.setTypeface(Typeface.MONOSPACE);
Bitmap bm = Bitmap.createBitmap(16, 16, Bitmap.Config.ALPHA_8);
float x = bm.getWidth();
float y = bm.getHeight();
Canvas c = new Canvas(bm);
c.drawText("Test", x, y, paint);
}
Is this code ok? If yes, how can I make this new bitmap visible on screen? I tried this code which produced an error
setContentView(c); //<- ERROR!
I am confused with the element Canvas as there is not such element in XML which I can use in the code.
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评论（2）
setContentView(View)需要一个View和 Canvas 不是View。我不确定您是否想自己创建一个
Canvas。不过，有多种方法可以获取从 Android 框架传递给您的Canvas。实现此目的的一种方法是创建自定义View。为此，您需要创建一个扩展View的新类。重写
View类时，您将能够重写onDraw(Canvas)方法。这可能是您想要在您发布的代码中的onCreate()方法中执行的操作。此链接很好地概述了创建您的自己的自定义视图。
setContentView(View)takes aViewand Canvas is not aView.I am not sure that you want to create a
Canvason your own. There are ways to get aCanvaspassed to you from the Android Framework though. One way you can do this is by creating a customView. To do this, you will need to create a new class that extendsView.When overriding a
Viewclass, you will have the ability to override theonDraw(Canvas)method. This is probably where you want to do what you are attempting to do in youronCreate()method in the code you posted.This link gives a good overview of what is required to create your own custom view.
第一：如果您在指定的 x 和 y 位置绘制文本，则会绘制它
在右下角，从该像素开始。您的画布上不会绘制任何内容。尝试 bm.getWidth()/2，高度与测试绘图相同。您可以稍后对其进行优化。
第二：Canvas不是View（不扩展View类）。您只能通过 set ContentView() 设置视图。我在这里建议编写一个仅包含单个 ImageView 的 XML 布局，并通过 setContentView(R.layout.mylayout) 进行设置。
之后，您可以使用 findViewById() 获取该 ImageView 并使用 ImageView.setImageBitmap(bm) 在其上显示您的位图。
使用位图创建画布后，您无需对画布执行任何操作。从那时起，您在画布内绘制的所有内容都会立即在位图中找到。
因此您不能在 XML 中指定 Canvas。可以这么说，它只是一个编辑图片的“编辑器”，而不是一个实际的 UI 元素。
First: If you draw your text at the x and y position you specified, you draw it
at the lower right corner, starting with exactly that pixel. Nothing will be drawn on your canvas. Try bm.getWidth()/2, for height the same for test drawing. You can optimize that later.
Second: Canvas is not a View (does not extend the View class). You can only set Views via set ContentView(). What I recommend here is writing a XML layout containing only a single ImageView and set that via setContentView(R.layout.mylayout).
After that, you can use findViewById() to grab that ImageView and use ImageView.setImageBitmap(bm) to show your bitmap on it.
You dont have to do anything with the canvas, once you created it with your bitmap. Everything you draw inside the canvas from that point on is found in the Bitmap immediately.
Therefore you can't specify the Canvas in XML. It's just an "Editor" to edit pictures, so to speak and not an actual UI element.