Question

我正在开发一个应用程序，我需要绘制并将其保存为sd卡中的图像

 public void onClickSave()
        {

            FrameLayout v = (FrameLayout) findViewById(R.id.main_frame);
            v.setDrawingCacheEnabled(true);

            v.measure(MeasureSpec.makeMeasureSpec(0, MeasureSpec.UNSPECIFIED), MeasureSpec.makeMeasureSpec(0, MeasureSpec.UNSPECIFIED));
            v.layout(0, 0, v.getWidth(), v.getHeight());
            v.buildDrawingCache(true);
            Bitmap bm = Bitmap.createBitmap(v.getDrawingCache());
            v.setDrawingCacheEnabled(false);
            if (bm != null) {
                try {
                    String path = Environment.getExternalStorageDirectory().toString();
                    OutputStream fOut = null;
                    File file = new File(path, "screentest.jpg");
                    fOut = new FileOutputStream(file);
                    bm.compress(Bitmap.CompressFormat.JPEG, 85, fOut);
                    fOut.flush();
                    fOut.close();                     
                }
                catch (Exception e) {
                    e.printStackTrace();
                    Toast.makeText(getContext(), e.toString(),1000).show();
                }
            }

并且函数调用在这里发生

 Button btn_save=(Button) findViewById(R.id.button3);
        btn_save.setOnClickListener(new OnClickListener() 
        {

            public void onClick(View v) 
            {
                // TODO Auto-generated method stub

                drawView.onClickSave();

            }
        });

我在日志中收到错误：

05-23 12:46:25.413: W/dalvikvm(669): threadid=1: thread exiting with uncaught exception (group=0x4001d800)
05-23 12:46:25.423: E/AndroidRuntime(669): FATAL EXCEPTION: main
05-23 12:46:25.423: E/AndroidRuntime(669): java.lang.NullPointerException
05-23 12:46:25.423: E/AndroidRuntime(669):  at com.page2.DrawView.onClickSave(DrawView.java:173)
05-23 12:46:25.423: E/AndroidRuntime(669):  at com.page2.Draw$3.onClick(Draw.java:60)
05-23 12:46:25.423: E/AndroidRuntime(669):  at android.view.View.performClick(View.java:2408)
05-23 12:46:25.423: E/AndroidRuntime(669):  at android.view.View$PerformClick.run(View.java:8816)
05-23 12:46:25.423: E/AndroidRuntime(669):  at android.os.Handler.handleCallback(Handler.java:587)
05-23 12:46:25.423: E/AndroidRuntime(669):  at android.os.Handler.dispatchMessage(Handler.java:92)
05-23 12:46:25.423: E/AndroidRuntime(669):  at android.os.Looper.loop(Looper.java:123)
05-23 12:46:25.423: E/AndroidRuntime(669):  at android.app.ActivityThread.main(ActivityThread.java:4627)
05-23 12:46:25.423: E/AndroidRuntime(669):  at java.lang.reflect.Method.invokeNative(Native Method)
05-23 12:46:25.423: E/AndroidRuntime(669):  at java.lang.reflect.Method.invoke(Method.java:521)
05-23 12:46:25.423: E/AndroidRuntime(669):  at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:868)
05-23 12:46:25.423: E/AndroidRuntime(669):  at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:626)
05-23 12:46:25.423: E/AndroidRuntime(669):  at dalvik.system.NativeStart.main(Native Method)

我的xml是

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="fill_parent"
android:layout_height="fill_parent"
android:orientation="vertical"
android:background="@android:color/white" >
<FrameLayout
 android:id="@+id/main_frame"
 android:layout_width="fill_parent"
 android:layout_height="fill_parent"
 android:background="@android:color/white" android:layout_weight="0.1">

<ImageView
     android:id="@+id/imageView1"
     android:layout_width="wrap_content"
     android:layout_height="wrap_content"
      /> 

</FrameLayout>
<RelativeLayout
 android:id="@+id/relativeLayout1"
 android:layout_width="match_parent"
 android:layout_height="match_parent"
   android:layout_weight="0.9" android:layout_gravity="bottom" android:layout_marginTop="-10dp">
 <Button
     android:id="@+id/button2"
     android:layout_width="wrap_content"
     android:layout_height="wrap_content"
     android:layout_alignParentBottom="true"
     android:layout_alignParentTop="true"
     android:layout_centerHorizontal="true"
     android:text="Redo" />
 <Button
     android:id="@+id/button1"
     android:layout_width="wrap_content"
     android:layout_height="wrap_content"
     android:layout_alignParentBottom="true"
     android:layout_alignParentLeft="true"
     android:layout_alignParentTop="true"
     android:text="Undo" />
 <Button
     android:id="@+id/button3"
     android:layout_width="wrap_content"
     android:layout_height="wrap_content"
     android:layout_alignParentBottom="true"
     android:layout_alignParentRight="true"
     android:layout_alignParentTop="true"
     android:text="Save" />
 </RelativeLayout>
</LinearLayout>This is my xml

给我一些其他方法将画布绘制作为图像存储在SD卡中当我点击保存按钮时我的应用程序强制关闭请帮助我在此先感谢

Answer 1

我会supsect

       FrameLayout v = (FrameLayout) findViewById(R.id.main_frame);

返回 null

使用调试器或记录

进行检查

当您的视图不包含FrameLayout时，它是

不是由您的xml
或“main_frame”已在其他功能中删除

如果此代码真的在第173行

  public void onClickSave()

比这更令人怀疑，因为没有访问参考。这可能是一些过时的代码和apk的暗示。尝试重建项目（项目 - ＆gt;清除日食）

Answer 2

在使用之前尝试构建绘图缓存：

v.buildDrawingCache();

在SD卡中保存图像画布Java Null指针异常

2 个答案: