1

我正在尝试将线性布局转换为位图。但它给出了一个空指针异常。我的代码是。

位图为空。因为我没有得到“不为空”的吐司。为什么我将位图设为空。我尝试了许多类似的问题，但那里的代码相同。

public class Receipt extends Activity {

    public Bitmap bitmap;
    LinearLayout layout;
    private String fileName;
    private File file;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        // TODO Auto-generated method stub
        super.onCreate(savedInstanceState);
        setContentView(R.layout.receipt);
        ImageView iv = (ImageView) findViewById(R.id.Ivsignature);
        iv.setImageBitmap(Signature.sign);

        layout = (LinearLayout) findViewById(R.id.Llreceipt);
        layout.setDrawingCacheEnabled(true);
        layout.buildDrawingCache();
        bitmap = layout.getDrawingCache(true);

        if (bitmap != null)
            Toast.makeText(getApplicationContext(), "not null",
                    Toast.LENGTH_LONG).show();
        String myPath = Environment.getExternalStorageDirectory()
                + "/signature_image";
        File myDir = new File(myPath);
        try {
            myDir.mkdirs();
        } catch (Exception e) {
        }

        String fname = fileName + "gwg" + ".jpg";
        file = new File(myDir, fname);
        FileOutputStream fos = null;
        try {
            fos = new FileOutputStream(file);
            bitmap.compress(CompressFormat.JPEG, 100, fos);
            Toast.makeText(getApplicationContext(), "File saved",
                    Toast.LENGTH_LONG).show();
        } catch (Exception e) {
            Toast.makeText(getApplicationContext(), String.valueOf(e),
                    Toast.LENGTH_LONG).show();
        }
    }
}
4

3 回答 3

4

您可以将视图绘制到使用位图实例化的画布上，以便将视图写入位图。绘制到该画布后，位图将包含视图。

确保在您的视图布局并实际具有宽度和高度后调用下面的函数

public Bitmap createBitmapForView(View view)
{
    int width = view.getWidth();
    int height = view.getHeight();

    // create a bitmap the size of the view
    Bitmap screenShot = Bitmap.createBitmap(width, height, Bitmap.Config.ARGB_8888);

    // create a canvas with the bitmap
    Canvas canvas = new Canvas(screenShot);

    // draw the view to the canvas
    view.draw(canvas);

    // now your bitmap contains the view
    return screenShot;
}
于 2012-10-18T14:12:32.820 回答
2

您不能在 onCreate 中执行此操作，因为尚未绘制视图。您可以在活动中使用 ViewTreeObserver 或覆盖 onAttachedToWindow()。

http://developer.android.com/reference/android/view/ViewTreeObserver.html

于 2012-10-18T14:00:38.193 回答
0 
package com.example.snapshotlayout;

import java.io.ByteArrayOutputStream;
import java.io.File;
import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.IOException;

import android.os.Bundle;
import android.os.Environment;
import android.app.Activity;
import android.graphics.Bitmap;
import android.view.View.MeasureSpec;
import android.widget.ImageView;
import android.widget.TextView;

public class SnapshotActivity extends Activity {

@Override
public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_snapshot);

    //initializing layouts
    TextView textView = (TextView)findViewById(R.id.textView);
    ImageView snapImage = (ImageView)findViewById(R.id.imageView);
    textView.setDrawingCacheEnabled(true);

    //specifying the dimensions of view
    textView.measure(MeasureSpec.makeMeasureSpec(0, MeasureSpec.UNSPECIFIED), 
          MeasureSpec.makeMeasureSpec(0, MeasureSpec.UNSPECIFIED));

    textView.layout(0, 0, textView.getMeasuredWidth(), textView.getMeasuredHeight()); 

    textView.buildDrawingCache(true);
    Bitmap b = Bitmap.createBitmap(textView.getDrawingCache());
    textView.setDrawingCacheEnabled(false); // clear drawing cache

    snapImage.setImageBitmap(b);   

    ByteArrayOutputStream bytes = new ByteArrayOutputStream();
    b.compress(Bitmap.CompressFormat.JPEG, 100, bytes);

    //create a new file in sdcard name it as "testimage.jpg"
    File fileImage = new File(Environment.getExternalStorageDirectory()
                            + File.separator + "testimage.jpg");

    //write the bytes in file
    FileOutputStream fo = null;
    try {
        fileImage.createNewFile();
        fo = new FileOutputStream(fileImage);
        fo.write(bytes.toByteArray());
    } catch (FileNotFoundException e) {
        e.printStackTrace();
    } catch (IOException e) {
        e.printStackTrace();
    }
}
}

这是xml文件的代码

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:orientation="vertical"
    android:id="@+id/snapLayout"
    android:layout_width="fill_parent"
    android:layout_height="fill_parent">
<TextView
    android:id="@+id/textView"
    android:layout_width="fill_parent"
    android:layout_height="wrap_content"
    android:text="Take snapshot of this layout"/>
<ImageButton  
    android:id="@+id/imageView"
    android:layout_width="fill_parent"
    android:layout_height="fill_parent"/>

</LinearLayout>

取自 http://hoodaandroid.blogspot.in/2012/09/taking-snapshot-or-screen-capture-of.html

于 2012-10-18T14:04:30.787 回答