Question

我的变量hz为null，为什么会这样？

代码：

        HorizontalScrollView hz = (HorizontalScrollView) findViewById((R.id.horizontalScrollView2));
        hz.addView(imageView, params);
        hz.setBackgroundColor(Color.BLACK);

// Show this layout in our activity.
        ScrollView scrollView = (ScrollView) findViewById(R.id.scrollView);
        setContentView(scrollView);

的xml：

<ScrollView
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    xmlns:android="http://schemas.android.com/apk/res/android"
    android:id="@+id/scrollView">

    <HorizontalScrollView
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:id="@+id/horizontalScrollView2">

        <AbsoluteLayout
            android:layout_width="1000dp"
            android:layout_height="1000dp"
            android:id="@+id/al"/>
    </HorizontalScrollView>

</ScrollView>

此外，它不允许我在horizontalScrollView中使用absoluteLayout。我试图制作一个比屏幕尺寸更大的可绘制区域，你可以上下滚动，我将绘制一个棋盘游戏板。有人可以帮我设置这个可绘制的区域吗？谢谢。

我活动的所有代码：

package com.example.btf.game;

import android.app.Activity;
import android.graphics.Bitmap;
import android.graphics.Canvas;
import android.graphics.Color;
import android.graphics.Paint;
import android.os.Bundle;
import android.widget.HorizontalScrollView;
import android.widget.ImageView;
import android.widget.RelativeLayout;
import android.widget.ScrollView;


public class SplashScreen extends Activity {



    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);

// We'll be creating an image that is 100 pixels wide and 200 pixels tall.
        int width = 1000;
        int height = 3000;

// Create a bitmap with the dimensions we defined above, and with a 16-bit pixel format. We'll
// get a little more in depth with pixel formats in a later post.
        Bitmap bitmap = Bitmap.createBitmap(width, height, Bitmap.Config.ARGB_8888);

// Create a paint object for us to draw with, and set our drawing color to blue.
        Paint paint = new Paint();
        paint.setColor(Color.BLUE);

// Create a new canvas to draw on, and link it to the bitmap that we created above. Any drawing
// operations performed on the canvas will have an immediate effect on the pixel data of the
// bitmap.
        Canvas canvas = new Canvas(bitmap);

// Fill the entire canvas with a red color.
        canvas.drawColor(Color.RED);

// Draw a rectangle inside our image using the paint object we defined above. The rectangle's
// upper left corner will be at (25,50), and the lower left corner will be at (75,150). Since we set
// the paint object's color above, this rectangle will be blue.
        canvas.drawRect(25, 50, 75, 150, paint);

// In order to display this image in our activity, we need to create a new ImageView that we
// can display.
        ImageView imageView = new ImageView(this);

// Set this ImageView's bitmap to the one we have drawn to.
        imageView.setImageBitmap(bitmap);

// Create a simple layout and add our image view to it.
        RelativeLayout layout = new RelativeLayout(this);
        RelativeLayout.LayoutParams params = new RelativeLayout.LayoutParams(RelativeLayout.LayoutParams.WRAP_CONTENT,
                RelativeLayout.LayoutParams.WRAP_CONTENT);
        params.addRule(RelativeLayout.CENTER_IN_PARENT);


        //  LinearLayout container = (LinearLayout) findViewById(R.id.container);
        HorizontalScrollView hz = (HorizontalScrollView) findViewById((R.id.horizontalScrollView2));
        hz.addView(imageView, params);
        hz.setBackgroundColor(Color.BLACK);

// Show this layout in our activity.
        ScrollView scrollView = (ScrollView) findViewById(R.id.scrollView);
        setContentView(scrollView);
    }
}

Answer 1

您的观点为空，因为您尝试通过findViewById()方法获取活动时没有活动的一部分。

您需要在“查找”视图之前致电setContentView()并在其中传递您的xml布局：setContentView(R.layout.my_acitivty_layout)

引用布局视图时出现空指针异常

1 个答案: