java - Android - 尝试创建 'Save file first?"对话框

Question

我的应用程序由文本文件列表组成。单击文件会将其加载到 EditText 中。我创建了一个选项菜单来保存打开的文件，或者像处理新文件一样保存。我想做的是显示“先保存？”如果用户尝试打开新文件而不先保存打开的文件，则会出现确认对话框。

正如您在下面的代码中看到的，我创建了一个名为“changed”的 boolean 变量，最初初始化为 false。我正在尝试使用 TextChangedListener 将更改更改为 true，然后使用列表的文件打开代码中的 if/else 语句处理它。我遇到的问题是，一旦我打开一个文件，然后尝试打开另一个文件，它会显示“首先保存”对话框，但无论文件是否更改，或者我单击“确定”或取消，它都不会打开任何文件其他文件。

public class MainActivity extends ListActivity {

private List<String> items = null;
public File currentDir = null;
public File currentFile = null;
public EditTextLineNumbers et; // My EditText
public boolean changed = false;

    @Override
    public void onCreate(Bundle icicle) {
        super.onCreate(icicle);
        setContentView(R.layout.main);

        checkExternalStorage();
        File dir = new File(Environment.getExternalStorageDirectory() + "/My Webs");
        currentDir = dir;
        et = (EditTextLineNumbers) findViewById(R.id.ide);
        et.addTextChangedListener(new TextWatcher() {

            @Override
            public void onTextChanged(CharSequence s, int start, int before, int count) {
                changed = true;
            }

            @Override
            public void beforeTextChanged(CharSequence s, int start, int count,
                    int after) {
                changed=false;

            }

            @Override
            public void afterTextChanged(Editable s) {
                // TODO Auto-generated method stub

            }
        });
        if(dir.isDirectory()) {
            getFiles(new File(Environment.getExternalStorageDirectory().getAbsolutePath() + "/My Webs").listFiles());
        }else{
            dir.mkdir();
        }
    }

    @Override
        public boolean onCreateOptionsMenu(Menu menu) {
            MenuInflater inflater = getMenuInflater();
            inflater.inflate(R.menu.menu, menu);
            return true;
        }

    @Override
        public boolean onOptionsItemSelected(MenuItem item) {
            if(item.getItemId()== R.id.newsite){
                Log.d("New Site","New Site was clicked");
            }else if(item.getItemId()== R.id.newfile){
                Log.d("New File","New File was clicked");
            }else if(item.getItemId()== R.id.savefile){
                String temptxt = et.getText().toString();

                if(currentFile!=null){
                    Log.d(currentFile.getAbsolutePath(),currentFile.getAbsolutePath());
                    String tempfname = currentFile.toString();
                    saveFile(tempfname, temptxt);
                }else{
                    saveFile(null, temptxt);
                }

            }
            return super.onOptionsItemSelected(item);
        }

    @Override
    protected void onListItemClick(ListView l, View v, int position, long id){
        int selectedRow = (int)id;
        if(selectedRow == 0){
            getFiles(new File(Environment.getExternalStorageDirectory().getAbsolutePath() + "/My Webs").listFiles());
        }else{
            File file = new File(items.get(selectedRow));
            if(file.isDirectory()){
                currentDir = file;
                getFiles(file.listFiles());
            }else{
                currentFile = file;
            if(changed==false){
                try {
                    et.setText(new Scanner(file).useDelimiter("\\Z").next());
                    } catch (FileNotFoundException e) {
                    // TODO Auto-generated catch block
                    e.printStackTrace();
                    }   
                }else{
                    AlertDialog.Builder alert = new AlertDialog.Builder(this);

                    alert.setTitle("Save first");
                    alert.setMessage("(Will be saved in the current working directory)");

                    alert.setPositiveButton("Ok", new DialogInterface.OnClickListener() {
                    public void onClick(DialogInterface dialog, int whichButton) {
                      String tmpText = et.getText().toString();

                      try {
                        File tempfile = new File(currentDir, currentFile.toString());
                        FileWriter writer = new FileWriter(tempfile);
                          writer.write(tmpText);
                          writer.flush();
                          writer.close();

                    } catch (IOException e) {
                        // TODO Auto-generated catch block
                        e.printStackTrace();
                    }
                      }
                    });

                    alert.setNegativeButton("Cancel", new DialogInterface.OnClickListener() {
                      public void onClick(DialogInterface dialog, int whichButton) {
                        // Canceled.
                      }
                    });

                    alert.show();

                }
            }
            }
        }


    private void saveFile(String sFileName, String sBody){

        if (currentFile!=null) {
            try {
                File saveDir = new File("/");

                File tempfile = new File(saveDir, sFileName);
                FileWriter writer = new FileWriter(tempfile);
                writer.append(sBody);
                writer.flush();
                writer.close();

                Toast.makeText(this, "Saved", Toast.LENGTH_SHORT).show();
            } catch (IOException e) {
                e.printStackTrace();
            }
        }else{
            saveAs();
        }

    }

    private void saveAs(){
        AlertDialog.Builder alert = new AlertDialog.Builder(this);

        alert.setTitle("Save as");
        alert.setMessage("(Will be saved in the current working directory)");

        // Set an EditText view to get user input 
        final EditText input = new EditText(this);
        alert.setView(input);

        alert.setPositiveButton("Ok", new DialogInterface.OnClickListener() {
        public void onClick(DialogInterface dialog, int whichButton) {
          String value = input.getText().toString();
          String tmpText = et.getText().toString();

          try {
            File tempfile = new File(currentDir, value);
            FileWriter writer = new FileWriter(tempfile);
              writer.write(tmpText);
              writer.flush();
              writer.close();

        } catch (IOException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
          }
        });

        alert.setNegativeButton("Cancel", new DialogInterface.OnClickListener() {
          public void onClick(DialogInterface dialog, int whichButton) {
            // Canceled.
          }
        });

        alert.show();
    }
        private void getFiles(File[] files){
            items = new ArrayList<String>();
            items.add(getString(R.string.goto_root));
            for(File file : files){
                String filename = file.getName().toString();
                String filenameArray[] = filename.split("\\.");
                String extension = filenameArray[filenameArray.length-1];
                Log.d("Extension", extension);
                items.add(file.getPath());
            }
            ArrayAdapter<String> fileList = new ArrayAdapter<String>(this,R.layout.row_item, items);
            setListAdapter(fileList);
        }

}

Answer 1

如果文本发生更改，您的变量 change 将始终为 true，因为事件 beforeTextChanged 将在 之后首先调用onTextChanged 将被触发。

beforeTextChanged(CharSequence s, int start, int count, int after) This method is called to notify you that, within s, the count characters beginning at start are about to be replaced by new text with length after.

onTextChanged(CharSequence s, int start, int before, int count) This method is called to notify you that, within s, the count characters beginning at start have just replaced old text that had length before.

保存文件后，您应该重置变量change为 false

if(!changed){
    // open the file
 }else{
    changed = false;
    // show the alert and save the file
 }