Android无法实例化活动组件信息
我在这里找到了一些类似帖子的回复，但是没有一个能够解决我的问题。我有一个带有两个活动的简单应用程序。在EntryActivity中，值被输入到EditText中，然后显示在DisplayActivity中。我相当肯定这两个活动在清单中都被正确分配，但它会在活动之间停止工作，导致标题错误。我试过搬几样东西，但一点运气都没有 入口活动：Android无法实例化活动组件信息,android,android-intent,Android,Android Intent,我在这里找到了一些类似帖子的回复，但是没有一个能够解决我的问题。我有一个带有两个活动的简单应用程序。在EntryActivity中，值被输入到EditText中，然后显示在DisplayActivity中。我相当肯定这两个活动在清单中都被正确分配，但它会在活动之间停止工作，导致标题错误。我试过搬几样东西，但一点运气都没有 入口活动： package com.natep.userentry; import android.os.Bundle; import android.app.Activity
package com.natep.userentry;
import android.os.Bundle;
import android.app.Activity;
import android.content.Intent;
import android.text.Editable;
import android.text.TextWatcher;
import android.util.Log;
import android.view.Menu;
import android.view.View;
import android.widget.EditText;
import android.widget.RadioGroup;
import android.widget.RadioButton;
import android.widget.Button;
public class EntryActivity extends Activity {
//Instantiate variables
public String sex = "";
public String firstName = "";
public String lastName = "";
public String age = "";
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_entry);
//Instantiate the EditTexts and assign listeners
EditText firstNameEditText = (EditText) findViewById(R.id.firstNameEditText);
firstNameEditText.addTextChangedListener(firstNameEditTextListener);
EditText lastNameEditText = (EditText) findViewById(R.id.lastNameEditText);
lastNameEditText.addTextChangedListener(lastNameEditTextListener);
EditText ageEditText = (EditText) findViewById(R.id.ageEditText);
ageEditText.addTextChangedListener(ageEditTextListener);
RadioButton radio_male = (RadioButton) findViewById(R.id.radio_male);
RadioButton radio_female = (RadioButton) findViewById(R.id.radio_female);
Button enterButton = (Button) findViewById(R.id.enterButton);
}
@Override
public boolean onCreateOptionsMenu(Menu menu) {
// Inflate the menu; this adds items to the action bar if it is present.
getMenuInflater().inflate(R.menu.entry, menu);
return true;
}
//Method for handling radio button input
public void radioButtonClicked(View view) {
// Is the button now checked?
boolean checked = ((RadioButton) view).isChecked();
// Check which radio button was clicked
switch(view.getId()) {
case R.id.radio_male:
if (checked)
sex = "Male";
break;
case R.id.radio_female:
if (checked)
sex = "Female";
break;
}
}
//Handles the First Name EditText
private TextWatcher firstNameEditTextListener = new TextWatcher()
{
@Override
public void onTextChanged(CharSequence s, int start, int before, int count)
{
try
{
firstName = s.toString();
}
catch (NumberFormatException e)
{
firstName = "";
}
}
@Override
public void beforeTextChanged(CharSequence arg0, int arg1, int arg2,
int arg3) {
// TODO Auto-generated method stub
}
@Override
public void afterTextChanged(Editable arg0)
{
}
};
//Handles the Last Name EditText
private TextWatcher lastNameEditTextListener = new TextWatcher()
{
@Override
public void onTextChanged(CharSequence s, int start, int before, int count)
{
try
{
lastName = s.toString();
}
catch (NumberFormatException e)
{
lastName = "";
}
}
@Override
public void beforeTextChanged(CharSequence arg0, int arg1, int arg2,
int arg3) {
// TODO Auto-generated method stub
}
@Override
public void afterTextChanged(Editable arg0)
{
}
};
//Handles the Age EditText
private TextWatcher ageEditTextListener = new TextWatcher()
{
@Override
public void onTextChanged(CharSequence s, int start, int before, int count)
{
try
{
age = s.toString();
}
catch (NumberFormatException e)
{
age = "";
}
}
@Override
public void beforeTextChanged(CharSequence arg0, int arg1, int arg2,
int arg3) {
// TODO Auto-generated method stub
}
@Override
public void afterTextChanged(Editable arg0)
{
}
};
//Define method to create intent on Button click
public void enterData(View view) {
Intent intent = new Intent(this, DisplayActivity.class);
intent.putExtra("FIRST_NAME", firstName);
intent.putExtra("LAST_NAME", lastName);
intent.putExtra("USER_AGE", age);
intent.putExtra("USER_SEX", sex) ;
startActivity(intent);
}
}
package com.natep.userentry;
import android.os.Bundle;
import android.app.Activity;
import android.content.Intent;
import android.view.Menu;
import android.widget.TextView;
public class DisplayActivity extends Activity {
//Instantiate the necessary TextViews
TextView firstTextView = (TextView) findViewById(R.id.firstTextView);
TextView lastTextView = (TextView) findViewById(R.id.lastTextView);
TextView ageDisplayTextView = (TextView) findViewById(R.id.ageTextView);
TextView sexDisplayTextView = (TextView) findViewById(R.id.sexDisplayTextView);
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_display);
//Receive the bundle from Entry activity
Intent intent = getIntent();
Bundle extras = intent.getExtras();
//Instantiate strings from Entry activity
String firstName = extras.getString("FIRST_NAME");
String lastName = extras.getString("LAST_NAME");
String age = extras.getString("USER_AGE");
String sex = extras.getString("USER_SEX");
//Populate the TextViews with strings from Bundle
firstTextView.setText(firstName);
lastTextView.setText(lastName);
ageDisplayTextView.setText(age);
sexDisplayTextView.setText(sex);
}
@Override
public boolean onCreateOptionsMenu(Menu menu) {
// Inflate the menu; this adds items to the action bar if it is present.
getMenuInflater().inflate(R.menu.display, menu);
return true;
}
}
<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
package="com.natep.userentry"
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.natep.userentry.EntryActivity"
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.natep.userentry.DisplayActivity"
android:label="@string/title_activity_display" >
</activity>
</application>
</manifest>
05-03 16:32:14.226: D/dalvikvm(1464): GC_FOR_ALLOC freed 59K, 6% free 2894K/3048K, paused 40ms, total 41ms
05-03 16:32:14.226: I/dalvikvm-heap(1464): Grow heap (frag case) to 3.497MB for 614416- byte allocation
05-03 16:32:14.296: D/dalvikvm(1464): GC_FOR_ALLOC freed 2K, 5% free 3491K/3652K, paused 59ms, total 59ms
05-03 16:32:14.856: D/gralloc_goldfish(1464): Emulator without GPU emulation detected.
05-03 16:32:23.506: W/IInputConnectionWrapper(1464): endBatchEdit on inactive InputConnection
05-03 16:32:26.146: I/Choreographer(1464): Skipped 30 frames! The application may be doing too much work on its main thread.
05-03 16:32:31.886: D/AndroidRuntime(1464): Shutting down VM
05-03 16:32:31.886: W/dalvikvm(1464): threadid=1: thread exiting with uncaught e exception (group=0xb3a14ba8)
05-03 16:32:31.926: E/AndroidRuntime(1464): FATAL EXCEPTION: main
05-03 16:32:31.926: E/AndroidRuntime(1464): Process: com.natep.userentry, PID: 1464
05-03 16:32:31.926: E/AndroidRuntime(1464): java.lang.RuntimeException: Unable to instantiate activity ComponentInfo{com.natep.userentry/com.natep.userentry.DisplayActivity}: java.lang.NullPointerException
05-03 16:32:31.926: E/AndroidRuntime(1464): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2121)
05-03 16:32:31.926: E/AndroidRuntime(1464): at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2245)
05-03 16:32:31.926: E/AndroidRuntime(1464): at android.app.ActivityThread.access$800(ActivityThread.java:135)
05-03 16:32:31.926: E/AndroidRuntime(1464): at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1196)
05-03 16:32:31.926: E/AndroidRuntime(1464): at android.os.Handler.dispatchMessage(Handler.java:102)
05-03 16:32:31.926: E/AndroidRuntime(1464): at android.os.Looper.loop(Looper.java:136)
05-03 16:32:31.926: E/AndroidRuntime(1464): at android.app.ActivityThread.main(ActivityThread.java:5017)
05-03 16:32:31.926: E/AndroidRuntime(1464): at java.lang.reflect.Method.invokeNative(Native Method)
05-03 16:32:31.926: E/AndroidRuntime(1464): at java.lang.reflect.Method.invoke(Method.java:515)
05-03 16:32:31.926: E/AndroidRuntime(1464): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:779)
05-03 16:32:31.926: E/AndroidRuntime(1464): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:595)
05-03 16:32:31.926: E/AndroidRuntime(1464): at dalvik.system.NativeStart.main(Native Method)
05-03 16:32:31.926: E/AndroidRuntime(1464): Caused by: java.lang.NullPointerException
05-03 16:32:31.926: E/AndroidRuntime(1464): at android.app.Activity.findViewById(Activity.java:1884)
05-03 16:32:31.926: E/AndroidRuntime(1464): at com.natep.userentry.DisplayActivity.<init>(DisplayActivity.java:12)
05-03 16:32:31.926: E/AndroidRuntime(1464): at java.lang.Class.newInstanceImpl(Native Method)
05-03 16:32:31.926: E/AndroidRuntime(1464): at java.lang.Class.newInstance(Class.java:1208)
05-03 16:32:31.926: E/AndroidRuntime(1464): at android.app.Instrumentation.newActivity(Instrumentation.java:1061)
05-03 16:32:31.926: E/AndroidRuntime(1464): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2112)
05-03 16:32:31.926: E/AndroidRuntime(1464): ... 11 more
05-03 16:32:35.216: I/Process(1464): Sending signal. PID: 1464 SIG: 9
05-03 16:32:14.226:D/dalvikvm（1464）：释放59K，6%释放2894K/3048K，暂停40ms，总计41ms
05-03 16:32:14.226:I/dalvikvm堆（1464）：为614416字节分配将堆（frag案例）增长到3.497MB
5-03 16:32:14.296:D/dalvikvm（1464）：释放2K的所有物质的GC_，5%的自由3491K/3652K，暂停59ms，总计59ms
05-03 16:32:14.856:D/gralloc_金鱼（1464）：未检测到GPU仿真的仿真器。
05-03 16:32:23.506:W/IIInputConnectionWrapper（1464）：在非活动InputConnection上进行endBatchEdit
05-03 16:32:26.146:I/编舞（1464）：跳过了30帧！应用程序可能在其主线程上做了太多工作。
05-03 16:32:31.886:D/AndroidRuntime（1464）：关闭虚拟机
05-03 16:32:31.886:W/dalvikvm（1464）：threadid=1：线程以未捕获的e异常退出（组=0xb3a14ba8）
05-03 16:32:31.926:E/AndroidRuntime（1464）：致命异常：主
05-03 16:32:31.926:E/AndroidRuntime（1464）：进程：com.natep.userentry，PID:1464
05-03 16:32:31.926:E/AndroidRuntime（1464）：java.lang.RuntimeException:无法实例化活动组件信息{com.natep.userentry/com.natep.userentry.DisplayActivity}:java.lang.NullPointerException
05-03 16:32:31.926:E/AndroidRuntime（1464）：在android.app.ActivityThread.performLaunchActivity（ActivityThread.java:2121）上
05-03 16:32:31.926:E/AndroidRuntime（1464）：位于android.app.ActivityThread.handleLaunchActivity（ActivityThread.java:2245）
05-03 16:32:31.926:E/AndroidRuntime（1464）：在android.app.ActivityThread.access$800（ActivityThread.java:135）
05-03 16:32:31.926:E/AndroidRuntime（1464）：在android.app.ActivityThread$H.handleMessage（ActivityThread.java:1196）
05-03 16:32:31.926:E/AndroidRuntime（1464）：位于android.os.Handler.dispatchMessage（Handler.java:102）
05-03 16:32:31.926:E/AndroidRuntime（1464）：在android.os.Looper.loop（Looper.java:136）
05-03 16:32:31.926:E/AndroidRuntime（1464）：位于android.app.ActivityThread.main（ActivityThread.java:5017）
05-03 16:32:31.926:E/AndroidRuntime（1464）：位于java.lang.reflect.Method.Invokenactive（本机方法）
05-03 16:32:31.926:E/AndroidRuntime（1464）：位于java.lang.reflect.Method.invoke（Method.java:515）
05-03 16:32:31.926:E/AndroidRuntime（1464）：在com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run（ZygoteInit.java:779）
05-03 16:32:31.926:E/AndroidRuntime（1464）：位于com.android.internal.os.ZygoteInit.main（ZygoteInit.java:595）
5-03 16:32:31.926:E/AndroidRuntime（1464）：在dalvik.system.NativeStart.main（本机方法）
05-03 16:32:31.926:E/AndroidRuntime（1464）：由以下原因引起：java.lang.NullPointerException
05-03 16:32:31.926:E/AndroidRuntime（1464）：在android.app.Activity.findViewById（Activity.java:1884）
05-03 16:32:31.926:E/AndroidRuntime（1464）：位于com.natep.userentry.DisplayActivity。（DisplayActivity.java:12）
05-03 16:32:31.926:E/AndroidRuntime（1464）：位于java.lang.Class.newInstanceImpl（本机方法）
05-03 16:32:31.926:E/AndroidRuntime（1464）：位于java.lang.Class.newInstance（Class.java:1208）
05-03 16:32:31.926:E/AndroidRuntime（1464）：在android.app.Instrumentation.newActivity（Instrumentation.java:1061）上
05-03 16:32:31.926:E/AndroidRuntime（1464）：在android.app.ActivityThread.performLaunchActivity（ActivityThread.java:2112）上
05-03 16:32:31.926:E/AndroidRuntime（1464）：。。。还有11个
05-03 16:32:35.216:I/进程（1464）：发送信号。PID:1464信号：9
onCreate（）的DisplayActivity
方法中：
TextView firstTextView = (TextView) findViewById(R.id.firstTextView);
TextView lastTextView = (TextView) findViewById(R.id.lastTextView);
TextView ageDisplayTextView = (TextView) findViewById(R.id.ageTextView);
TextView sexDisplayTextView = (TextView) findViewById(R.id.sexDisplayTextView);
将findViewById（）调用从成员变量初始化移动到setContentView（）之后的onCreate（）。在onCreate（）之前，没有窗口，您将获得此NPE。在setContentView（）之前，你找不到任何东西。你能发布错误日志吗？我发布了错误日志作为编辑。嗯，我确实觉得自己像个傻瓜。这就解决了。谢谢你的帮助。