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[英]Android: Setting onClickListener to a Part of text in a TextView - Issue
[英]android TextView set text issue
我是android
新手,并试图显示一条从意图中作为额外字符串传递的消息,代码如下:
public class DisplayMessageActivity extends /*Activity*/ActionBarActivity {
@SuppressLint("NewApi")
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
Intent intent = getIntent();
String message = intent.getStringExtra(MainActivity.EXTRA_MESSAGE);
TextView textView = (TextView) findViewById(R.id.display_message);
textView.setTextSize(40);
textView.setText(message);
setContentView(R.layout.activity_display_message);
setupActionBar();
}
/**
* Set up the {@link android.app.ActionBar}, if the API is available.
*/
@TargetApi(Build.VERSION_CODES.HONEYCOMB)
private void setupActionBar() {
if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.HONEYCOMB) {
getActionBar().setDisplayHomeAsUpEnabled(true);
}else{
getSupportActionBar().setDisplayHomeAsUpEnabled(true);
}
}
@Override
public boolean onCreateOptionsMenu(Menu menu) {
getMenuInflater().inflate(R.menu.display_message, menu);
return true;
}
@Override
public boolean onOptionsItemSelected(MenuItem item) {
switch (item.getItemId()) {
case android.R.id.home:
NavUtils.navigateUpFromSameTask(this);
return true;
}
return super.onOptionsItemSelected(item);
}
}
我得到如下错误:
01-27 23:45:05.864: E/AndroidRuntime(528): FATAL EXCEPTION: main
01-27 23:45:05.864: E/AndroidRuntime(528): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.myfirstapp/com.example.myfirstapp.DisplayMessageActivity}: java.lang.NullPointerException
01-27 23:45:05.864: E/AndroidRuntime(528): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1956)
01-27 23:45:05.864: E/AndroidRuntime(528): at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:1981)
01-27 23:45:05.864: E/AndroidRuntime(528): at android.app.ActivityThread.access$600(ActivityThread.java:123)
01-27 23:45:05.864: E/AndroidRuntime(528): at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1147)
01-27 23:45:05.864: E/AndroidRuntime(528): at android.os.Handler.dispatchMessage(Handler.java:99)
01-27 23:45:05.864: E/AndroidRuntime(528): at android.os.Looper.loop(Looper.java:137)
01-27 23:45:05.864: E/AndroidRuntime(528): at android.app.ActivityThread.main(ActivityThread.java:4424)
01-27 23:45:05.864: E/AndroidRuntime(528): at java.lang.reflect.Method.invokeNative(Native Method)
01-27 23:45:05.864: E/AndroidRuntime(528): at java.lang.reflect.Method.invoke(Method.java:511)
01-27 23:45:05.864: E/AndroidRuntime(528): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:784)
01-27 23:45:05.864: E/AndroidRuntime(528): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:551)
01-27 23:45:05.864: E/AndroidRuntime(528): at dalvik.system.NativeStart.main(Native Method)
01-27 23:45:05.864: E/AndroidRuntime(528): Caused by: java.lang.NullPointerException
01-27 23:45:05.864: E/AndroidRuntime(528): at com.example.myfirstapp.DisplayMessageActivity.onCreate(DisplayMessageActivity.java:29)
01-27 23:45:05.864: E/AndroidRuntime(528): at android.app.Activity.performCreate(Activity.java:4465)
01-27 23:45:05.864: E/AndroidRuntime(528): at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1049)
01-27 23:45:05.864: E/AndroidRuntime(528): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1920)
01-27 23:45:05.864: E/AndroidRuntime(528): ... 11 more
我还已在strings.xml
中将display_message
定义为<string name="display_message">Display a message</string>
,并在活动中启用操作栏的overlay
模式,并设置android:paddingTop="?attr/actionBarSize"
为活动布局文件。 所以我想知道如何解决问题?
干杯
检索UI元素之前,请移动setContentView
。
即,您需要先膨胀您的布局,否则findViewById
返回null
,因此在textView.setTextSize(40);
行处textView.setTextSize(40);
NullPointerException
textView.setTextSize(40);
。
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_display_message);
/****/
TextView textView = (TextView) findViewById(R.id.display_message);
textView.setTextSize(40);
textView.setText(message);
首先:
setContentView(R.layout.activity_display_message);
此方法用于通过活动引用布局,因此在将活动与布局链接后,需要获取布局UI引用,因此需要在setContentView
方法之后移动所有UI引用
第二:
此代码
Intent intent = getIntent();
String message = intent.getStringExtra(MainActivity.EXTRA_MESSAGE);
您需要首先检查intent是否包含额外的数据,如果intent没有数据,则会导致null指针异常,因为您想通过添加此代码来访问null对象的getStringExtra
,从而可以防止此错误
Intent intent = getIntent();
if(intent.getExtras() !=null){
String message = intent.getStringExtra(MainActivity.EXTRA_MESSAGE);
}
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