Question

我必须参加活动，第一个活动包含一个EditText＆amp;一个按钮，当我按下按钮时，在EditText字段中输入的值应该转移到另一个活动中的TextView，但是当我运行应用程序时，请输入一些文字和点击按钮，应用程序崩溃＆amp;模拟器显示错误，我尝试了很多东西，但不知道问题是什么

第一个活动代码：

 package com.example.sqa;

 import android.os.Bundle;
 import android.app.Activity;
 import android.content.Intent;
 import android.view.Menu;
 import android.view.View;
   import android.view.View.OnClickListener;
   import android.widget.*;
   public class TheFirst extends Activity {


TextView tv1;
     EditText ed1;
     Button b1;

     @Override
     protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_the_first);
        tv1=(TextView)findViewById(R.id.textView1);
        ed1=(EditText)findViewById(R.id.editText1);
        b1=(Button)findViewById(R.id.button1);

        final Intent i1=new Intent(TheFirst.this,TheSecond.class);
        String temp=ed1.getText().toString();
        i1.putExtra("v1", temp);

        b1.setOnClickListener(new OnClickListener() {

            @Override
            public void onClick(View arg0) {
                startActivity(i1);

            }
        });

     }

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

  }

SECONDE ACTIVITY CODE：

   package com.example.sqa;

   import android.os.Bundle;
   import android.app.Activity;
   import android.content.Intent;
   import android.view.Menu; 
   import android.view.View;
   import android.view.View.OnClickListener;
   import android.widget.Button;
   import android.widget.TextView;

   public class TheSecond extends Activity {


    TextView tv2;
    Button b2;

     @Override
     protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_the_second);
        tv2=(TextView)findViewById(R.id.textView2);
        b2=(Button)findViewById(R.id.button2);

        Intent i2=getIntent();
        tv2.setText(i2.getStringExtra("v1"));

        b2.setOnClickListener(new OnClickListener() {

            @Override
            public void onClick(View arg0) {
                Intent i1=new Intent(TheSecond.this,TheFirst.class);
                startActivity(i1);

            }
            });
    }

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

    }

AndroidManifest.xml文件：

    <?xml version="1.0" encoding="utf-8"?>
    <manifest xmlns:android="http://schemas.android.com/apk/res/android"
     package="com.example.sqa"
     android:versionCode="1"
     android:versionName="1.0" >

     <uses-sdk
         android:minSdkVersion="8"
         android:targetSdkVersion="18" />

     <application
         android:allowBackup="true"
         android:icon="@drawable/ic_launcher"
         android:label="@string/app_name"
         android:theme="@style/AppTheme" >



         <activity
            android:name="com.example.sqa.TheFirst"
             android:label="@string/app_name" >
             <intent-filter>
                 <action android:name="android.intent.action.MAIN" />
                 <category android:name="android.intent.category.LAUNCHER" />
             </intent-filter>
         </activity>



         <activity
             android:name="com.example.sqa.TheSecond"
             android:label="@string/title_activity_the_second" >
         </activity>


     </application>

    </manifest>

logcat的：

   04-10 19:12:31.070: D/dalvikvm(1714): GC_FOR_ALLOC freed 89K, 5% free 3279K/3440K, paused 45ms, total 48ms
   04-10 19:12:31.130: D/gralloc_goldfish(1714): Emulator without GPU emulation detected.
   04-10 19:12:37.530: D/AndroidRuntime(1714): Shutting down VM
   04-10 19:12:37.530: W/dalvikvm(1714): threadid=1: thread exiting with uncaught exception (group=0xb1afdb90)
   04-10 19:12:37.580: E/AndroidRuntime(1714): FATAL EXCEPTION: main
   04-10 19:12:37.580: E/AndroidRuntime(1714): Process: com.example.sqa, PID: 1714
   04-10 19:12:37.580: E/AndroidRuntime(1714): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.sqa/com.example.sqa.TheSecond}: java.lang.NullPointerException
   04-10 19:12:37.580: E/AndroidRuntime(1714):  at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2176)
   04-10 19:12:37.580: E/AndroidRuntime(1714):  at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2226)
   04-10 19:12:37.580: E/AndroidRuntime(1714):  at android.app.ActivityThread.access$700(ActivityThread.java:135)
   04-10 19:12:37.580: E/AndroidRuntime(1714):  at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1397)
   04-10 19:12:37.580: E/AndroidRuntime(1714):  at android.os.Handler.dispatchMessage(Handler.java:102)
   04-10 19:12:37.580: E/AndroidRuntime(1714):  at android.os.Looper.loop(Looper.java:137)
   04-10 19:12:37.580: E/AndroidRuntime(1714):  at android.app.ActivityThread.main(ActivityThread.java:4998)
   04-10 19:12:37.580: E/AndroidRuntime(1714):  at java.lang.reflect.Method.invokeNative(Native Method)
   04-10 19:12:37.580: E/AndroidRuntime(1714):  at java.lang.reflect.Method.invoke(Method.java:515)
   04-10 19:12:37.580: E/AndroidRuntime(1714):  at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:777)
   04-10 19:12:37.580: E/AndroidRuntime(1714):  at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:593)
   04-10 19:12:37.580: E/AndroidRuntime(1714):  at dalvik.system.NativeStart.main(Native Method)
   04-10 19:12:37.580: E/AndroidRuntime(1714): Caused by: java.lang.NullPointerException
   04-10 19:12:37.580: E/AndroidRuntime(1714):  at com.example.sqa.TheSecond.onCreate(TheSecond.java:26)
   04-10 19:12:37.580: E/AndroidRuntime(1714):  at android.app.Activity.performCreate(Activity.java:5243)
   04-10 19:12:37.580: E/AndroidRuntime(1714):  at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1087)
   04-10 19:12:37.580: E/AndroidRuntime(1714):  at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2140)
   04-10 19:12:37.580: E/AndroidRuntime(1714):  ... 11 more
   04-10 19:13:03.340: I/Process(1714): Sending signal. PID: 1714 SIG: 9

activity_the_first.xml：

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    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"
    tools:context=".TheFirst" >

    <TextView
        android:id="@+id/textView1"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_alignParentTop="true"
        android:layout_centerHorizontal="true"
        android:layout_marginTop="38dp"
        android:textAppearance="?android:attr/textAppearanceLarge" />

    <EditText
        android:id="@+id/editText1"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_below="@+id/textView1"
        android:layout_centerHorizontal="true"
        android:layout_marginTop="48dp"
        android:ems="10"
        android:hint="@string/s2" >

        <requestFocus />
    </EditText>

    <Button
        android:id="@+id/button1"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_centerHorizontal="true"
        android:layout_centerVertical="true"
        android:text="@string/s3" />


   <TextView
    android:id="@+id/textView2"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:layout_alignTop="@+id/textView1"
    android:layout_centerHorizontal="true"
    android:text="@string/s1"
    android:textAppearance="?android:attr/textAppearanceLarge" />

</RelativeLayout>

activity_the_second.xml：

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    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"
    tools:context=".TheSecond" >

    <TextView
        android:id="@+id/textView1"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_alignParentTop="true"
        android:layout_centerHorizontal="true"
        android:layout_marginTop="40dp"
        android:text="@string/s4"
        android:textAppearance="?android:attr/textAppearanceLarge" />

    <Button
        android:id="@+id/button2"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_below="@+id/textView1"
        android:layout_centerHorizontal="true"
        android:layout_marginTop="66dp"
        android:text="@string/s3" />

</RelativeLayout>

Answer 1

首先移动此

 String temp=ed1.getText().toString();

在按钮onclick()内部，例如：

 b1.setOnClickListener(new OnClickListener() {

        @Override
        public void onClick(View arg0) {
            String temp=ed1.getText().toString();
            i1.putExtra("v1", temp);
            startActivity(i1);

        }
    });

Answer 2

您确定以下内容是否正确？

b2=(Button)findViewById(R.id.button1);

R.id.button1还是其他什么？

Answer 3

在您的第二个活动中替换此行。 tv2.setText（i2.getStringExtra（＆＃34; V1＆＃34））; 至 String text = getIntent（）。getExtras（）。getString（＆＃34; vi＆＃34;）; tv2.setText（文本）;

Answer 4

确保textView 2存在于activity.xml

中

Answer 5

我觉得现在一切都很清楚，冲突的ID 我没有注意到这一点因为我使用Eclipse＆amp;我通常不会使用默认ID ＆安培;这是我第一次处理多项活动，所以看起来eclipse在一个布局中给对象提供了不同的ID，＆amp;一旦我创建了另一个活动布局，它再次提供相同的ID，尽管两个布局都在同一个项目中。谢谢所有人。

Android-错误使用putExtra（String name，String value）方法时

5 个答案: