我正在尝试遵循此post的建议:
但是当我运行此代码时,我的程序崩溃了。这是我的代码:
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
/* Change the font for the password hint to match that of the
* user name field */
EditText pw = (EditText) findViewById(R.id.password);
pw.setTypeface(Typeface.DEFAULT); //<---Crashes on this line
pw.setTransformationMethod(new PasswordTransformationMethod());
setContentView(R.layout.activity_main);
}
以下是此对象的XML:
<EditText
android:id="@+id/password"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_alignLeft="@+id/userName"
android:layout_alignRight="@+id/appName"
android:layout_below="@+id/userName"
android:layout_marginTop="14dp"
android:ems="10"
android:hint="@string/password"
android:inputType="textPassword" />
最后,这里是LogCat输出,我可以看到错误:
05-09 00:30:21.408:E / Trace(16987):错误打开跟踪文件:没有这样的 文件或目录(2)05-09 00:30:21.918:D / AndroidRuntime(16987): 关闭VM 05-09 00:30:21.918:W / dalvikvm(16987):threadid = 1: 线程退出与未捕获的异常(组= 0x40a71930)05-09 00:30:21.978:E / AndroidRuntime(16987):致命异常:主05-09 00:30:21.978:E / AndroidRuntime(16987):java.lang.RuntimeException: 无法开始活动 ComponentInfo {com.mobilenicity.gen_co_event_marketing_app / com.mobilenicity.gen_co_event_marketing_app.MainActivity}: java.lang.NullPointerException 05-09 00:30:21.978: E / AndroidRuntime(16987):at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2180) 05-09 00:30:21.978:E / AndroidRuntime(16987):at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2230) 05-09 00:30:21.978:E / AndroidRuntime(16987):at android.app.ActivityThread.access $ 600(ActivityThread.java:141)05-09 00:30:21.978:E / AndroidRuntime(16987):at android.app.ActivityThread $ H.handleMessage(ActivityThread.java:1234) 05-09 00:30:21.978:E / AndroidRuntime(16987):at android.os.Handler.dispatchMessage(Handler.java:99)05-09 00:30:21.978:E / AndroidRuntime(16987):at android.os.Looper.loop(Looper.java:137)05-09 00:30:21.978: E / AndroidRuntime(16987):at android.app.ActivityThread.main(ActivityThread.java:5041)05-09 00:30:21.978:E / AndroidRuntime(16987):at java.lang.reflect.Method.invokeNative(Native Method)05-09 00:30:21.978:E / AndroidRuntime(16987):at java.lang.reflect.Method.invoke(Method.java:511)05-09 00:30:21.978: E / AndroidRuntime(16987):at com.android.internal.os.ZygoteInit $ MethodAndArgsCaller.run(ZygoteInit.java:793) 05-09 00:30:21.978:E / AndroidRuntime(16987):at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:560)05-09 00:30:21.978:E / AndroidRuntime(16987):at dalvik.system.NativeStart.main(Native Method)05-09 00:30:21.978: E / AndroidRuntime(16987):引起:java.lang.NullPointerException 05-09 00:30:21.978:E / AndroidRuntime(16987):at com.mobilenicity.gen_co_event_marketing_app.MainActivity.onCreate(MainActivity.java:26) 05-09 00:30:21.978:E / AndroidRuntime(16987):at android.app.Activity.performCreate(Activity.java:5104)05-09 00:30:21.978:E / AndroidRuntime(16987):at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1080) 05-09 00:30:21.978:E / AndroidRuntime(16987):at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2144) 05-09 00:30:21.978:E / AndroidRuntime(16987):... 11更多
无法弄清楚出了什么问题。谁能看到它?谢谢!
答案 0 :(得分:1)
更改setContentView(R.layout.activity_main);
在 super.onCreate(savedInstanceState);
<小时/> 当您执行
EditText pw = (EditText) findViewById(R.id.password);
时,findViewById
“无法检索您在EditText
中定义的layout
(因为您之后调用了setContentView
)因此findViewById
返回null,当您执行pw.setTypeface(Typeface.DEFAULT);
时,它会抛出NPE
因为pw为null
。