无法将位图保存在手机内存中
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【中文标题】无法将位图保存在手机内存中【英文标题】：Cannot save bitmap on phone memory 【发布时间】：2012-08-16 14:46:47 【问题描述】：我在以下代码中得到位图 b 的 java null 异常：我该怎么办？ 为什么 getDrawingCache 函数在创建位图时不起作用； 启动动作的按钮的 onClickListener：
KaufenGListener = new OnClickListener()
@Override
public void onClick(View v)
Coupon coupon = null;
System.out.println("-- iv: " + couponView);
if (clickedcoup == -1)
Toast.makeText(getActivity(), "Please select a coupon", Toast.LENGTH_SHORT).show();
else
for (int i = 0; i < coupons.size(); i++)
if (clickedcoup == i)
coupon = coupons.get(i);
String username;
Bitmap coupo = BitmapFactory.decodeResource(getResources(), R.drawable.coupon1);
Bitmap barcode = Util.generateEAN("9310779300005", getActivity(), coupo.getWidth() / 3);
// Drawable couponDraw = new
// BitmapDrawable(getResources(),b);
System.out.println("------------b : " + barcode);
if (user.address.Nachname != null)
username = user.address.Nachname + " " + user.address.Vorname; // bla
else
username = "";
viewFlipperVino.setDisplayedChild(8);
// LayoutParams params = new LayoutParams();
// params.width=LayoutParams.MATCH_PARENT;
// params.height=(int) (params.width/1.5);
//couponView.buildDrawingCache();
couponView.setUp(coupo, barcode, coupon.Code, gutscheinName, username, coupon.Wert);
clickedcoup = -1;
String[] recipients = new String[] "rosu_alin@ymail.com" ;
String emailSubject = "Gutschein Schenken fur "+ gutscheinName;
String emailText = "Glückwunsch, Sie haben einen Gutschein für Wein & Co!!";
Intent intent = new Intent(Intent.ACTION_SEND);
intent.setType("plain/text");
intent.putExtra(Intent.EXTRA_EMAIL, recipients);
intent.putExtra(Intent.EXTRA_SUBJECT, emailSubject);
intent.putExtra(Intent.EXTRA_TEXT, emailText);
File root = Environment.getExternalStorageDirectory();
File file = new File(root, "gutschein.png");
try
file.createNewFile();
catch (IOException e1)
e1.printStackTrace();
couponView.setDrawingCacheEnabled(true);
couponView.buildDrawingCache();
Bitmap b = couponView.getDrawingCache();
System.out.println("bitmapget drawin cache: "+couponView.getDrawingCache());
Saver.saveImg(file, b, getActivity());
try
System.out.println("bitmap"+b);
FileOutputStream out = new FileOutputStream(file);
b.compress(Bitmap.CompressFormat.PNG, 100, out);
System.out.println("bitmap.compress"+b.compress(Bitmap.CompressFormat.PNG, 100, out));
catch (Exception e)
e.printStackTrace();
if (!file.exists() || !file.canRead())
Toast.makeText(getActivity(), "Befestigung Fehler", Toast.LENGTH_SHORT).show();
return;
Uri uri = Uri.parse("file://" + file);
intent.putExtra(Intent.EXTRA_STREAM, uri);
startActivity(Intent.createChooser(intent, "Send email..."));
;
这是扩展 View 的 CouponView 类： 公共类 CouponView 扩展视图
private Bitmap coupon, barcode;
Paint paint = new Paint();
Paint paint2 = new Paint();
Paint paint3 = new Paint();
private String name;
private String code;
private String username;
private String wert;
int w;
int h;
public CouponView(Context context, AttributeSet attrs, int defStyle)
super(context, attrs, defStyle);
init();
public CouponView(Context context, AttributeSet attrs)
super(context, attrs);
init();
public CouponView(Context context)
super(context);
init();
private void init()
paint.setColor(0xFF000000);
paint.setTextSize(7);
paint2.setColor(0xFF000000);
paint2.setTextSize(10);
paint3.setColor(0xFF000000);
paint3.setTextSize(25);
public void setUp(Bitmap coupon, Bitmap barcode, String code, String name, String username,String wert)
this.coupon = coupon;
this.barcode = barcode;
this.name = name;
this.username = username;
this.code = code;
this.wert = wert;
w = coupon.getWidth();
h = coupon.getHeight();
System.out.println("height"+h);
System.out.println("width"+w);
invalidate();
@Override
protected void onDraw(Canvas canvas)
super.onDraw(canvas);
System.out.println("-------------CouponView.onDraw()");
canvas.drawBitmap(coupon, 0, 0, null);
canvas.drawBitmap(barcode, w/1.61f, h/1.20f, null);
canvas.drawText("9310779300005", w/1.429f, h/1.018f, paint);
canvas.drawText("9310779300005", w/18.12f , h/1.073f, paint2);
canvas.drawText(code, w/1.8875f, h/1.073f, paint2);
canvas.drawText(username, w/11.32f, h/10.3f, paint2);
canvas.drawText(name, w/11.32f, h/5.936f, paint2);
canvas.drawText(wert, w/1.294f, h/1.641f, paint3);
按照我的逻辑，我将 couponView 的绘图缓存设置为 (true)，然后我开始构建绘图缓存。然后我启动位图getDrawingCache()。仅此一项就可以保存我的文件。我错过了什么？ Saves.saveIMG 函数的作用与之后的 try catch 相同（我只从同事那里拿了它，因为它更有条理。虽然它使用 imageView 来保存，而不是位图。
public class Saver
public static void saveImg(File pic, Bitmap picture,Context context)
folderExists(pic);
try
FileOutputStream out = new FileOutputStream(pic);
picture.compress(Bitmap.CompressFormat.JPEG, 100, out);
Log.i(Saver.class.toString(), " picture writed at: " + pic.getAbsolutePath());
Toast.makeText(context, "pic saved", Toast.LENGTH_SHORT).show();
catch (Exception e)
pic.delete();
Log.i(Saver.class.toString(), " picture writing error: " + e.getMessage());
Toast.makeText(context, "pic not saved", Toast.LENGTH_SHORT).show();
private static void folderExists(File dir)
System.out.println("-=-=- : " + dir.getAbsolutePath());
if (!dir.getParentFile().exists())
dir.mkdirs();
【问题讨论】：
哪行代码抛出了NullPointerException？
b.compress(Bitmap.CompressFormat.PNG, 100, out);
但是 System.out.prinln("bitmap=",b);行返回位图=空，所以我猜是位图 b 是问题，因为 getDrawingCache 没有加载它
嗯？ System.out.println 在 android 中什么都不做，***.com/questions/2220547/…
我的，观察你的 LogCat，看看 Syso 写在那里
【参考方案1】：
不确定您的代码到底出了什么问题，但这对我来说可以保存和读取手机内存中的位图：
将位图写入内存：
public void writeBitmapToMemory(String filename, Bitmap bitmap)
FileOutputStream fos;
// Use the compress method on the Bitmap object to write image to the OutputStream
try
fos = this.openFileOutput(filename, Context.MODE_PRIVATE);
// Writing the bitmap to the output stream
bitmap.compress(Bitmap.CompressFormat.PNG, 100, fos);
fos.close();
catch (FileNotFoundException e)
e.printStackTrace();
catch (IOException e)
e.printStackTrace();
阅读：
public Bitmap readBitmapFromMemory(String filename)
Bitmap defautBitmap = null;
File filePath = this.getFileStreamPath(filename);
FileInputStream fi;
try
fi = new FileInputStream(filePath);
defautBitmap = BitmapFactory.decodeStream(fi);
catch (FileNotFoundException e)
e.printStackTrace();
return defautBitmap;
我希望这会有所帮助。
【讨论】：
问题是位图从一开始就是空的。所以我认为我做的那部分代码没问题，或者至少它没有错误。我的代码的问题是从 imageView (couponView) 获取位图。那边出了点问题，没有正确创建我的位图【参考方案2】：我首先创建了一个空位图，并将其用作画布进行绘制。 代码：
couponView.setDrawingCacheEnabled(true);
couponView.buildDrawingCache();
couponView.setUp(coupo, barcode, coupon.Code, gutscheinName, username, coupon.Wert);
Bitmap b = Bitmap.createBitmap(couponView.w, couponView.h,
Config.ARGB_8888);
Canvas canvas = new Canvas(b);
couponView.draw(canvas);
Saver.saveImg(file, b, getActivity());
Uri uri = Uri.parse("file://" + file);
intent.putExtra(Intent.EXTRA_STREAM, uri);
startActivity(Intent.createChooser(intent, "Send email..."));
【讨论】：
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