Question

我正在尝试从Android项目中的assets文件夹中读取文件，但无法使其正常工作。我正在尝试这样的事情：

public class MainActivity extends AppCompatActivity {

    TextView fileContentTextView;
    StringBuilder stringBuilder;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        fileContentTextView = findViewById(R.id.file_content_textview);

        stringBuilder = new StringBuilder();

        AsyncTask.execute(new Runnable() {
            @Override
            public void run() {
                AssetManager assetManager = getBaseContext().getAssets();
                try {
                    InputStream inputStream = assetManager.open("cos.txt");
                    BufferedReader bufferedReader = new BufferedReader(new InputStreamReader(inputStream));
                    String str;
                    str = bufferedReader.readLine();
                    stringBuilder.append(str);
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
        });
        Log.d("ECG", stringBuilder.toString());
        String textToShow = stringBuilder.toString();
        fileContentTextView.setText(textToShow);
    }
}

但是在日志或尝试设置setText时没有任何显示。不知道我在做什么错。

谢谢。

Answer 1

我不确定为什么需要使用AsyncTask.execute（）。正如CommonsWare的注释所解释的那样，它在后台线程（与主UI线程分开）中执行。因此，stringbuilder.append（str）稍后被调用，而Log.d("ECG", stringBuilder.toString()); String textToShow = stringBuilder.toString(); fileContentTextView.setText(textToShow);被更快地调用。

因此，有两种方法可以纠正此问题：

从AsysncTask.execute（）中删除代码，如下所示：

public class MainActivity extends AppCompatActivity {

    TextView fileContentTextView;
    StringBuilder stringBuilder;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        fileContentTextView = findViewById(R.id.file_content_textview);

        stringBuilder = new StringBuilder();


        AssetManager assetManager = getBaseContext().getAssets();
        try {
            InputStream inputStream = assetManager.open("cos.txt");
            BufferedReader bufferedReader = new BufferedReader(new InputStreamReader(inputStream));
            String str;
            str = bufferedReader.readLine();
            stringBuilder.append(str);
        } catch (IOException e) {
            e.printStackTrace();
        }

        Log.d("ECG", stringBuilder.toString());
        String textToShow = stringBuilder.toString();
        fileContentTextView.setText(textToShow);
    }
}

放入log.d和fileContentTextView.setText（textToShow）;在AsyncTask.execute（）里面

public class MainActivity extends AppCompatActivity {

    TextView fileContentTextView;
    StringBuilder stringBuilder;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        fileContentTextView = findViewById(R.id.file_content_textview);

        stringBuilder = new StringBuilder();

        AsyncTask.execute(new Runnable() {
            @Override
            public void run() {
                AssetManager assetManager = getBaseContext().getAssets();
                try {
                    InputStream inputStream = assetManager.open("cos.txt");
                    BufferedReader bufferedReader = new BufferedReader(new InputStreamReader(inputStream));
                    String str;
                    str = bufferedReader.readLine();
                    stringBuilder.append(str);
                    Log.d("ECG", stringBuilder.toString());
                    String textToShow = stringBuilder.toString();
                    fileContentTextView.setText(textToShow);
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
        });

    }
}

我都测试过，他们都为我工作。

无法使用BufferedReader读取文件

1 个答案: