错误：任务“：app：mergeDebugAssets”执行失败

Question

我正在尝试在 Android Studio 中创建一个应用程序，当我点击一个按钮时，它会打开一个保存在应用程序资产文件夹中的 PDF 文件。它通过意图通过 3rd 方应用程序打开 PDF。

当我尝试运行它时遇到此错误：

错误：任务 ':app:mergeDebugAssets' 执行失败。

java.lang.NullPointerException（没有错误信息）

我的 MainActivity.java 代码是：

public class MainActivity extends AppCompatActivity {

public void showPDF(View view) {
    Toast.makeText(MainActivity.this, "button pressed", Toast.LENGTH_LONG).show();
    //startActivity(new Intent(Intent.ACTION_VIEW, Uri.parse("pdfurl.pdf")));
    AssetManager assetManager = getAssets();
    File file = new File(getFilesDir(), "myfile.pdf");
    try {
        InputStream in = assetManager.open("myfile.pdf");
        OutputStream out = openFileOutput(file.getName(), 1);
        copyFile(in, out);
        in.close();
        out.flush();
        out.close();
    } catch (Exception e) {
    }
    Intent intent = new Intent("android.intent.action.VIEW");
    intent.setDataAndType(Uri.parse("file://" + getFilesDir() + "/myfile.pdf"), "application/pdf");
    startActivity(intent);
}

private void copyFile(InputStream in, OutputStream out) throws IOException {
    byte[] buffer = new byte[AccessibilityNodeInfoCompat.ACTION_NEXT_HTML_ELEMENT];
    while (true) {
        int read = in.read(buffer);
        if (read != -1) {
            out.write(buffer, 0, read);
        } else {
            return;
        }
    }
}




@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);
}
}

做什么？

Answer 1

来自 Stackoverflow 问题Read a pdf file from assets folder

附言尝试四处搜索您的答案，以免重复。 :)

public class SampleActivity extends Activity
{

    @Override
    protected void onCreate(Bundle savedInstanceState)
    {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);
        CopyReadAssets();
    }

    private void CopyReadAssets(View v)
    {
        AssetManager assetManager = getAssets();

        InputStream in = null;
        OutputStream out = null;
        File file = new File(getFilesDir(), "abc.pdf");
        try
        {
            in = assetManager.open("abc.pdf");
            out = openFileOutput(file.getName(), Context.MODE_WORLD_READABLE);

            copyFile(in, out);
            in.close();
            in = null;
            out.flush();
            out.close();
            out = null;
        } catch (Exception e)
        {
            Log.e("tag", e.getMessage());
        }

        Intent intent = new Intent(Intent.ACTION_VIEW);
        intent.setDataAndType(
                Uri.parse("file://" + getFilesDir() + "/abc.pdf"),
                "application/pdf");

        startActivity(intent);
    }

    private void copyFile(InputStream in, OutputStream out) throws IOException
    {
        byte[] buffer = new byte[1024];
        int read;
        while ((read = in.read(buffer)) != -1)
        {
            out.write(buffer, 0, read);
        }
    }
}

如果这不起作用！让我知道！但请记住，环顾四周，也许您会发现您的问题已经得到解答。