Android Studio中印的EditText返回null

Question

我創建了一個簡單的應用程序在用戶輸入他們的名字和得分這應該是一個整數只，然後單擊按鈕，它應該來自這兩個的EditText框的數據打印到日誌。問題是我得到的是Null，而Score是零。

//主

import android.os.Bundle; 
import android.support.design.widget.FloatingActionButton; 
import android.support.design.widget.Snackbar; 
import android.support.v7.app.AppCompatActivity; 
import android.support.v7.widget.Toolbar; 
import android.view.View; 
import android.view.Menu; 
import android.view.MenuItem; 
import android.widget.Button; 
import android.widget.EditText; 

public class MainActivity extends AppCompatActivity { 
    Button SaveDataButton; 
    EditText TextName, TextScore; 
    String Name; 
    int Score; 


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

     FloatingActionButton fab = (FloatingActionButton) findViewById(R.id.fab); 
     fab.setOnClickListener(new View.OnClickListener() { 
      @Override 
      public void onClick(View view) { 
       Snackbar.make(view, "Replace with your own action", Snackbar.LENGTH_LONG) 
         .setAction("Action", null).show(); 

       SaveDataButton = (Button) findViewById(R.id.button); 
       TextName = (EditText) findViewById(R.id.editText1); 
       TextScore = (EditText) findViewById(R.id.editText2); 
       Name = TextName.getText().toString(); 
       Score = Integer.parseInt(TextScore.getText().toString()); 

      } 
     }); 
    } 


    public void SaveDataOnClick (View view){ 
     System.out.println(Name); 
     System.out.println(Score); 
    } 

    @Override 
    public boolean onCreateOptionsMenu(Menu menu) { 
     // Inflate the menu; this adds items to the action bar if it is present. 
     getMenuInflater().inflate(R.menu.menu_main, menu); 
     return true; 
    } 

    @Override 
    public boolean onOptionsItemSelected(MenuItem item) { 
     // Handle action bar item clicks here. The action bar will 
     // automatically handle clicks on the Home/Up button, so long 
     // as you specify a parent activity in AndroidManifest.xml. 
     int id = item.getItemId(); 

     //noinspection SimplifiableIfStatement 
     if (id == R.id.action_settings) { 
      return true; 
     } 

     return super.onOptionsItemSelected(item); 
    } 
} 

//佈局

<?xml version="1.0" encoding="utf-8"?> 
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android" 
    xmlns:app="http://schemas.android.com/apk/res-auto" 
    xmlns:tools="http://schemas.android.com/tools" 
    android:layout_width="match_parent" 
    android:layout_height="match_parent" 
    android:paddingBottom="@dimen/activity_vertical_margin" 
    android:paddingLeft="@dimen/activity_horizontal_margin" 
    android:paddingRight="@dimen/activity_horizontal_margin" 
    android:paddingTop="@dimen/activity_vertical_margin" 
    app:layout_behavior="@string/appbar_scrolling_view_behavior" 
    tools:context="com.example.capstoneproject.module08courseproject_datastorage.MainActivity" 
    tools:showIn="@layout/activity_main"> 

    <LinearLayout 
     android:orientation="vertical" 
     android:layout_width="match_parent" 
     android:layout_height="match_parent" 
     android:layout_below="@+id/textView3" 
     android:layout_alignParentLeft="true" 
     android:layout_alignParentStart="true" 
     android:layout_marginTop="31dp" 
     android:weightSum="1"> 

     <TextView 
      android:layout_width="wrap_content" 
      android:layout_height="wrap_content" 
      android:textAppearance="?android:attr/textAppearanceMedium" 
      android:text="Name" 
      android:id="@+id/textView" /> 

     <EditText 
      android:layout_width="match_parent" 
      android:layout_height="wrap_content" 
      android:id="@+id/editText1" 
      android:layout_gravity="center_horizontal" /> 

     <TextView 
      android:layout_width="wrap_content" 
      android:layout_height="wrap_content" 
      android:textAppearance="?android:attr/textAppearanceMedium" 
      android:text="Score" 
      android:id="@+id/textView2" /> 

     <EditText 
      android:layout_width="match_parent" 
      android:layout_height="wrap_content" 
      android:id="@+id/editText2" 
      android:layout_gravity="center_horizontal" /> 

     <Button 
      android:layout_width="wrap_content" 
      android:layout_height="wrap_content" 
      android:text="Save Data" 
      android:id="@+id/button" 
      android:layout_gravity="center_horizontal" 
      android:onClick="SaveDataOnClick" /> 

    </LinearLayout> 

    <TextView 
     android:layout_width="wrap_content" 
     android:layout_height="wrap_content" 
     android:textAppearance="?android:attr/textAppearanceLarge" 
     android:text="Name and Score Data Storage" 
     android:id="@+id/textView3" 
     android:layout_alignParentTop="true" 
     android:layout_centerHorizontal="true" /> 

</RelativeLayout> 

//輸出

11-29 22:07:01.846 3192-3192/? I/System.out: null 
11-29 22:07:01.846 3192-3192/? I/System.out: 0 

Answer 1

編輯，因爲我錯過了一個事實，即你在匿名onClickListener讓您的小工具連線到你的FloatingActionButton。這些更改來解決這個問題：

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

    FloatingActionButton fab = (FloatingActionButton) findViewById(R.id.fab); 
    fab.setOnClickListener(new View.OnClickListener() { 
    @Override 
    public void onClick(View view) { 
     Snackbar.make(view, "Replace with your own action", Snackbar.LENGTH_LONG) 
     .setAction("Action", null).show(); 

     // remove all the widget stuff and move it outside 
    } 
    }); 

    SaveDataButton = (Button) findViewById(R.id.button); 
    TextName = (EditText) findViewById(R.id.editText1); 
    TextScore = (EditText) findViewById(R.id.editText2); 
    //Name = TextName.getText().toString(); 
    //Score = Integer.parseInt(TextScore.getText().toString()); 

} 

你把它寫在的方式是，最後5行以上代碼只執行，如果浮動操作按鈕（在材料設計應用程序的右下角的圓形按鈕）被點擊。我不認爲這是你的預期行爲。相反，當您想要獲取您的小部件引用並在活動管理器調用onCreate()時保留它們。

我註釋掉最後兩行，因爲此時在這兩個編輯文本值爲null。這對名稱沒有用處，並導致數字格式例外（您不能將null轉換爲數字）。

最後，我想你婉當用戶點擊「保存數據」按鈕，得到的實際值，因此修改SaveDataOnClick方法。請記住，每次單擊/輕敲按鈕時都會調用此方法，因此無論編輯文本字段中的當前值如何，都會調用此方法。事情是這樣的：

public void SaveDataOnClick (View view){ 
    Name = TextName.getText().toString(); 
    Score = Integer.parseInt(TextScore.getText().toString()); 
    System.out.println(Name); 
    System.out.println(Score); 
} 

我做了這些改變，這裏是我的日誌輸出：

11-29 22:44:22.696 20997-20997/? I/System.out: bobby 
11-29 22:44:22.696 20997-20997/? I/System.out: 123