Question

我是一名新手程序员，可能会超越自己，但到目前为止我编写的代码似乎无法正常工作，而且我一直在努力解决这个问题

问题在于，当我运行此应用程序时，TextView仍然显示为空。

public class MainActivity extends Activity
{
// GUI controls
TextView thoughtLogView;

/** Called when the activity is first created. */
@Override
public void onCreate(Bundle savedInstanceState)
{
    super.onCreate(savedInstanceState);
    //Set MainActivity.xml as user interface layout
    setContentView(R.layout.main);
    // bind GUI elements with local controls

    thoughtLogView = (TextView) findViewById(R.id.logTextView);
}

private String GetPhoneAddress() {
    File file = new File(Environment.getExternalStorageDirectory() + "mythoughtlog.txt");
    if (!file.exists()){
        String line = "Need to add smth";
        return line;
    }
    String line = null;
    //Read text from file
    //StringBuilder text = new StringBuilder();
    try {
        BufferedReader br = new BufferedReader(new FileReader(file));
        line = br.readLine();
    }
    catch (IOException e) {
        //You'll need to add proper error handling here
    }

    final TextView tvphone = (TextView) findViewById(R.id.logTextView);
    String saved_phone = GetPhoneAddress();
    if (saved_phone.length()>0){
        tvphone.setText(saved_phone);
    }
    return line;
}

这是布局文件：

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout
xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="fill_parent"
android:layout_height="fill_parent"
android:gravity="top|center"
android:orientation="vertical">

<TextView
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:text="@string/title"
    android:textStyle="normal"
    android:gravity="center"
    android:layout_marginTop="10dp"
    android:textSize="20sp"
    android:textColor="#FFFFFF"/>

<TextView
    android:layout_width="242dp"
    android:layout_height="227dp"
    android:id="@+id/logTextView"
    android:background="#ffffff" />

<LinearLayout
    android:layout_width="fill_parent"
    android:layout_height="fill_parent"
    android:gravity="bottom|center">

    <Button
        android:layout_height="80dp"
        android:text="New Log"
        android:layout_width="match_parent"
        android:layout_weight="1.0"
        android:textSize="25sp"
        android:onClick="onNewLogButtonClick"/>

</LinearLayout>

Answer 1

你没有打电话GetPhoneAddress()这就是你无法设置文本的原因。所以用这种方式改变你的代码。

public void onCreate(Bundle savedInstanceState)
{
    super.onCreate(savedInstanceState);
    //Set MainActivity.xml as user interface layout
    setContentView(R.layout.main);
    // bind GUI elements with local controls

    thoughtLogView = (TextView) findViewById(R.id.logTextView);
    GetPhoneAddress();
}

Answer 2

只有在执行完整方法后，才会从方法GetPhoneAddress()获取String结果。

问题在于，当我运行此应用程序时，TextView仍然显示为空。

这是因为saved_phone没有任何价值，而且您也没有调用GetPhoneAddress()，所以我建议您将这些代码行移到方法GetPhoneAddress()之外，正确调用它在将字符串设置为TextView之前检查字符串。

String saved_phone = GetPhoneAddress();
    if (saved_phone.length()>0){
        tvphone.setText(saved_phone);
    }

Answer 3

将此行移至

var Base = React.createClass({
  getInitialState() {
    return {current: 1}
  },
  render() {
    return (
      <div>{this.state.current}</div>
      <div>{this.props.children}</div>
      <div>{this.props.demo}</div>
    );
  }
});

export default connect(state => ({
  demo: state.demo
}))(Base);

---

var A = React.createClass({
  componentDidMount() {
    // how to set base class state
    //

    this.props.setDemo('demo');
  },
  render() {
     ....
  }
});

export default connect(() => ({}), {
  setDemo
});

问题是你目前正在尝试从return方法本身返回字符串GetPhoneAddress（）之前返回语句所以它什么都不返回，你需要在调用GetPhoneAddress（）之后设置文本，你可以实现上面的

无法让TextView显示来自txt文件的文本

3 个答案: