java.lang.RuntimeException:无法启动活动
我正试图研究如何为Android制作应用程序。 根据修改后的教程,我得到了这个错误java.lang.RuntimeException:无法启动活动,java,android,android-activity,Java,Android,Android Activity,我正试图研究如何为Android制作应用程序。 根据修改后的教程,我得到了这个错误 12-26 10:42:23.848: D/dalvikvm(1302): GC_CONCURRENT freed 362K, 15% free 2737K/3216K, paused 70ms+89ms, total 204ms 12-26 10:42:23.898: D/AndroidRuntime(1302): Shutting down VM 12-26 10:42:23.898: W/dalvikvm(
12-26 10:42:23.848: D/dalvikvm(1302): GC_CONCURRENT freed 362K, 15% free 2737K/3216K, paused 70ms+89ms, total 204ms
12-26 10:42:23.898: D/AndroidRuntime(1302): Shutting down VM
12-26 10:42:23.898: W/dalvikvm(1302): threadid=1: thread exiting with uncaught exception (group=0x40a70930)
12-26 10:42:23.928: E/AndroidRuntime(1302): FATAL EXCEPTION: main
12-26 10:42:23.928: E/AndroidRuntime(1302): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.startactivity/com.example.startactivity.DisplayMessageActivity}: java.lang.NullPointerException
12-26 10:42:23.928: E/AndroidRuntime(1302): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2180)
12-26 10:42:23.928: E/AndroidRuntime(1302): at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2230)
12-26 10:42:23.928: E/AndroidRuntime(1302): at android.app.ActivityThread.access$600(ActivityThread.java:141)
12-26 10:42:23.928: E/AndroidRuntime(1302): at android.app.ActivityThread$H.handleMessage(ActivityThread.java: 1234)
12-26 10:42:23.928: E/AndroidRuntime(1302): at android.os.Handler.dispatchMessage(Handler.java:99)
12-26 10:42:23.928: E/AndroidRuntime(1302): at android.os.Looper.loop(Looper.java:137)
12-26 10:42:23.928: E/AndroidRuntime(1302): at android.app.ActivityThread.main(ActivityThread.java:5039)
12-26 10:42:23.928: E/AndroidRuntime(1302): at java.lang.reflect.Method.invokeNative(Native Method)
12-26 10:42:23.928: E/AndroidRuntime(1302): at java.lang.reflect.Method.invoke(Method.java:511)
12-26 10:42:23.928: E/AndroidRuntime(1302): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:793)
12-26 10:42:23.928: E/AndroidRuntime(1302): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:560)
12-26 10:42:23.928: E/AndroidRuntime(1302): at dalvik.system.NativeStart.main(Native Method)
12-26 10:42:23.928: E/AndroidRuntime(1302): Caused by: java.lang.NullPointerException
12-26 10:42:23.928: E/AndroidRuntime(1302): at com.example.startactivity.DisplayMessageActivity.onCreate(DisplayMessageActivity.java:20)
12-26 10:42:23.928: E/AndroidRuntime(1302): at android.app.Activity.performCreate(Activity.java:5104)
12-26 10:42:23.928: E/AndroidRuntime(1302): at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1080)
12-26 10:42:23.928: E/AndroidRuntime(1302): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2144)
12-26 10:42:23.928: E/AndroidRuntime(1302): ... 11 more
12-26 10:43:11.418: I/Process(1302): Sending signal. PID: 1302 SIG: 9
这是主活动的代码
公共类MainActivity扩展活动{
公共最终静态字符串EXTRA_MESSAGE=“com.example.startactivity.MESSAGE”;
@凌驾
创建时受保护的void(Bundle savedInstanceState){
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
}
@凌驾
公共布尔onCreateOptions菜单(菜单){
//为菜单充气;这会将项目添加到操作栏(如果存在)。
getMenuInflater().充气(R.menu.activity\u主菜单);
返回true;
}
公共无效发送消息(查看){
Intent Intent=新的Intent(这个,DisplayMessageActivity.class);
EditText edit_nome=(EditText)findViewById(R.id.edit_nome);
EditText edit_cognome=(EditText)findViewById(R.id.edit_cognome);
Bundle=新Bundle();
bundle.putString(“nome”,编辑_nome.getText().toString());
bundle.putString(“cognome”,edit_cognome.getText().toString());
intent.putExtra(额外消息,捆绑包);
星触觉(意向);
}
}
这是DisplayMessageActivity的代码
public类DisplayMessageActivity扩展活动{
@凌驾
创建时受保护的void(Bundle savedInstanceState){
super.onCreate(savedInstanceState);
setContentView(R.layout.activity\u display\u message);
//在操作栏中显示“向上”按钮。
getActionBar().setDisplayHomeAsUpEnabled(true);
Intent=getIntent();
字符串nome=intent.getBundleExtra(“nome”).toString();
字符串cognome=intent.getBundleExtra(“cognome”).toString();
TextView textNome=新的TextView(此);
TextView textCognome=新的TextView(此);
textNome.setTextSize(40);
textCognome.setTextSize(40);
textNome.setText(nome);
textCognome.setText(cognome);
setContentView(textNome);
setContentView(textCognome);
}
@凌驾
公共布尔值onOptionsItemSelected(菜单项项){
开关(item.getItemId()){
案例android.R.id.home:
NavUtils.navigateUpFromSameTask(本);
返回true;
}
返回super.onOptionsItemSelected(项目);
}
}
谢谢您的帮助。将主活动代码更改为
public class MainActivity extends Activity {
public final static String EXTRA_MESSAGE = "com.example.startactivity.MESSAGE";
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
Intent intent = new Intent(this,DisplayMessageActivity.class);
EditText edit_nome = (EditText) findViewById(R.id.edit_nome);
EditText edit_cognome = (EditText) findViewById(R.id.edit_cognome);
Bundle bundle = new Bundle();
bundle.putString("nome", edit_nome.getText().toString());
bundle.putString("cognome", edit_cognome.getText().toString());
intent.putExtra(EXTRA_MESSAGE, bundle);
startActivity(intent);
}
@Override
public boolean onCreateOptionsMenu(Menu menu) {
// Inflate the menu; this adds items to the action bar if it is present.
getMenuInflater().inflate(R.menu.activity_main, menu);
return true;
}
}
确保清单文件中的条目:
<activity android:name=".DisplayMessageActivity"></activity>
logcat在以下位置显示问题:- com.example.startactivity/com.example.startactivity.DisplayMessageActivity 因此,最好的猜测是,在DisplayMessageActivity的TexView中设置文本的位置,nome和cognome值可能为null 尝试在包含文本的行中添加调试点
String nome = intent.getBundleExtra("nome").toString();
并查看是否存在任何空值
希望您调用的是
捆绑包的toString
方法,而不是检索其中存储的字符串。此外,您正在尝试获取一个包含存储在其中的密钥的捆绑包。试试chaning
String nome = intent.getBundleExtra("nome").toString();
String cognome = intent.getBundleExtra("cognome").toString();
到
考虑到如果接收到的意图不是您的,并且没有捆绑包
,或者没有其他捆绑包,那么您的nome
和cognome
字符串将是null
,而不是空字符串。问题不是运行时异常,它是一个简单的NPE。请看给出的行号,其中有些内容为空。@ForcelTA您是否尝试过下面发布的解决方案。那会解决你的问题。谢谢,太棒了。谢谢你的帮助
Bundle bundle = intent.getBundleExtra(MainActivity.EXTRA_MESSAGE);
if (bundle != null) {
String nome = bundle.getString("nome");
String cognome = bundle.getString("cognome");
}