Android，从不同的 Activity 在缓存中保存和加载位图

Question

我有一个需要在新 Activity 中显示的位图，所以我缓存它并在打开的 Activity 中尝试加载它，但我得到一个 nullPointerException。我在这里保存图像:

File cacheDir = getBaseContext().getCacheDir();
File f = new File(cacheDir, "pic");

try {
    FileOutputStream out = new FileOutputStream(
            f);
    pic.compress(
            Bitmap.CompressFormat.JPEG,
            100, out);
    out.flush();
    out.close();

} catch (FileNotFoundException e) {
    e.printStackTrace();
} catch (IOException e) {
    e.printStackTrace();
}

Intent intent = new Intent(
        AndroidActivity.this,
        OpenPictureActivity.class);
startActivity(intent);

然后在新 Activity 中我尝试打开它:

public void onCreate(Bundle icicle) {
    super.onCreate(icicle);

    File cacheDir = getBaseContext().getCacheDir();
    File f = new File(cacheDir, "pic");     
    FileInputStream fis = null;
    try {
        fis = new FileInputStream(f);
    } catch (FileNotFoundException e) {
        // TODO Auto-generated catch block
        e.printStackTrace();
    }
    Bitmap bitmap = BitmapFactory.decodeStream(fis);

    ImageView viewBitmap = (ImageView) findViewById(R.id.icon2);
    viewBitmap.setImageBitmap(bitmap);
    setContentView(R.layout.open_pic_layout);

Answer 1

只需检查您的代码:

ImageView viewBitmap = (ImageView) findViewById(R.id.icon2);
viewBitmap.setImageBitmap(bitmap);
setContentView(R.layout.open_pic_layout);

您在设置内容 View 之前编写了 findViewById()。这是错误的。

public void onCreate(Bundle icicle) {
    super.onCreate(icicle);
    setContentView(R.layout.open_pic_layout);

  // do your operations here
  }