Question

我想首先说我是一个大新手，我只在这里工作了大约4天，其中包括阅读java参考书的许多页面。

这个应用程序的目的是从文本文件中获取信息，然后用它做很少的数学运算然后返回一个值。我已经在运行android 5.1.1的计算机上运行模拟器，但是当我在运行6.0.1的笔记4上运行它时，它只是在调试模式下跳过代码行，我不明白为什么。

public class MainActivity extends AppCompatActivity implements View.OnClickListener {

    TextView output;

    EditText food;
    EditText block;
    EditText ounce;

    Button calculate_blocks;
    Button calculate_ounces;

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



        //finding elements
        output = (TextView) findViewById(R.id.output);

        food = (EditText) findViewById(R.id.food);
        block = (EditText) findViewById(R.id.blocks);
        ounce = (EditText) findViewById(R.id.ounces);

        calculate_ounces = (Button) findViewById(R.id.calculate_ounces);
        calculate_blocks = (Button) findViewById(R.id.calculate_blocks);


        //setting listeners
        calculate_blocks.setOnClickListener(this);
        calculate_ounces.setOnClickListener(this);
    }

    @Override
    public void onClick(View v) {


        final String FILENAME = android.os.Environment.getExternalStorageDirectory().getPath() + "/Foods.txt";

        BufferedReader fin = null;
        FileReader fr = null;

        String currentLine="zeutn", line=null ;
        String strfood = food.getText().toString();
        double gramsOfNutrientPerOunce=0;
        double ounces=0,blocks=0;

        try {
            ounces = Double.parseDouble(ounce.getText().toString());
        }   catch(NumberFormatException nfe){
            ounces=0;
        }

        try {
            blocks = Double.parseDouble(block.getText().toString());
        }   catch(NumberFormatException nfe){
            blocks=0;
        }


        //Find refrence value after food in file

        try {
            File file1 = new File(FILENAME);
            file1.createNewFile();
            fr = new FileReader(FILENAME);
            fin = new BufferedReader(fr);

            while ((currentLine = fin.readLine()) != null) {
                if ((currentLine.toUpperCase()).equals(strfood.toUpperCase())) {
                    line = fin.readLine();
                    fr.close();
                    fin.close();
                } else
                    output.setText("Add food to file");
            }

        }   catch (IOException e) {
            output.setText("Fail");
            }


        try{
            gramsOfNutrientPerOunce=Double.parseDouble(line);
        }   catch(NumberFormatException nfe){
            output.setText("Add food to file");
        }

        String out;
        double tmp;
        switch (v.getId()) {
            case R.id.calculate_blocks:
                tmp = ounces/gramsOfNutrientPerOunce;
                out=Double.toString(tmp);

                output.setText(out);
                break;

            case R.id.calculate_ounces:
                tmp = blocks*gramsOfNutrientPerOunce;
                out=Double.toString(tmp);

                output.setText(out);
                break;
        }
    }
}

任何帮助都表示抱歉，如果我这样做也是错误的，那么如果您需要更多信息或任何我愿意提供的信息。请提前感谢您！

Answer 1

您需要拥有Api等级23（Android 6.0）及更高版本的运行时权限。你可以这样做很简单。

// Here, thisActivity is the current activity
if (ContextCompat.checkSelfPermission(thisActivity,
            Manifest.permission.READ_EXTERNAL_STORAGE)
    != PackageManager.PERMISSION_GRANTED) {

    // Should we show an explanation?
    if (ActivityCompat.shouldShowRequestPermissionRationale(thisActivity,
        Manifest.permission.READ_EXTERNAL_STORAGE)) {

        // Show an explanation to the user *asynchronously* -- don't block
        // this thread waiting for the user's response! After the user
        // sees the explanation, try again to request the permission.

    } else {

        // No explanation needed, we can request the permission.

        ActivityCompat.requestPermissions(thisActivity,
            new String[]{Manifest.permission.READ_EXTERNAL_STORAGE},
            MY_PERMISSIONS_REQUEST_READ_EXTERNAL_STORAGE);

        // MY_PERMISSIONS_REQUEST_READ_EXTERNAL_STORAGE is an
        // app-defined int constant. The callback method gets the
        // result of the request.
    }
}

然后用户提供的响应可以在回调方法中处理它，就像这样。

@Override
public void onRequestPermissionsResult(int requestCode,
        String permissions[], int[] grantResults) {
    switch (requestCode) {
        case MY_PERMISSIONS_REQUEST_READ_EXTERNAL_STORAGE: {
            // If request is cancelled, the result arrays are empty.
            if (grantResults.length > 0
                    && grantResults[0] == PackageManager.PERMISSION_GRANTED) {

                // permission was granted, yay! Do the
                // contacts-related task you need to do.

            } else {

                // permission denied, boo! Disable the
                // functionality that depends on this permission.
            }
            return;
        }

        // other 'case' lines to check for other
        // permissions this app might request
    }
}

注意：编码样本取自https://developer.android.com

我注意到的另一件事是你有setOnClickListeners到你的按钮，但在你的onClick方法中你没有处理它，所以单击时按钮将执行完全相同的事情。您只需通过切换view.getID或在您的情况下使用v.getID来处理它们，代码就是这样的。

switch (v.getId()){

    case R.id.(id_of_firstButton):
        //do what you have to do for first button
        break;
    case R.id.(id_of_secondButton):
        //do what you have to do for second button
        break;
    default:
        //do something in the default case
        break; 
}

Answer 2

我不知道哪些行正在跳过，但似乎缺少读/写权限。

您需要使用Android 6.0及更高版本检查运行时的权限。

Documentation For Runtime Permissions.

Android在程序中跳过代码行

2 个答案: