Question

logcat的：

**FATAL EXCEPTION: main
Process: com.atg.antivirusnew, PID: 22956
Theme: themes:{default=overlay:system, iconPack:system, fontPkg:system, com.android.systemui=overlay:system, com.android.systemui.navbar=overlay:system}
java.lang.RuntimeException: Unable to start activity ComponentInfo{com.atg.antivirusnew/com.atg.antivirusnew.owaspguard.OWASP_MainActivity}: java.lang.NullPointerException: Attempt to invoke virtual method 'void android.app.ActionBar.setDisplayHomeAsUpEnabled(boolean)' on a null object reference
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2450)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2510)
at android.app.ActivityThread.-wrap11(ActivityThread.java)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1363)
at android.os.Handler.dispatchMessage(Handler.java:102)
at android.os.Looper.loop(Looper.java:148)
at android.app.ActivityThread.main(ActivityThread.java:5461)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:726)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:616)
Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'void android.app.ActionBar.setDisplayHomeAsUpEnabled(boolean)' on a null object reference
at com.atg.antivirusnew.owaspguard.OWASP_MainActivity.onCreate(OWASP_MainActivity.java:254)
at android.app.Activity.performCreate(Activity.java:6251)
at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1108)
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2403)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2510) 
at android.app.ActivityThread.-wrap11(ActivityThread.java) 
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1363) 
at android.os.Handler.dispatchMessage(Handler.java:102) 
at android.os.Looper.loop(Looper.java:148) 
at android.app.ActivityThread.main(ActivityThread.java:5461) 
at java.lang.reflect.Method.invoke(Native Method) 
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:726) 
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:616)**

代码：

 drawerToggle = new ActionBarDrawerToggle(this, drawerLayout,
                    toolbar, android.R.string.ok, android.R.string.ok) {
                public void onDrawerClosed(View view) {
            `enter code here`        getActionBar().setTitle(title);
                    invalidateOptionsMenu();
                }
                public void onDrawerOpened(View drawerView) {
                    getActionBar().setTitle(drawerTitle);
                    invalidateOptionsMenu();
                }
            };
            drawerLayout.addDrawerListener(drawerToggle);
            getActionBar().setDisplayHomeAsUpEnabled(true);
            getActionBar().setHomeButtonEnabled(true);

Answer 1

你应该这样做

 ((AppCompatActivity) getActivity()).getSupportActionBar().setDisplayHomeAsUpEnabled(true);

Answer 2

在使用... // we'll assume header is in row 1 but you can override with header_row in GET/POST data var headRow = e.parameter.header_row || 1; var callback = e.parameter.callback; // required for JSONP ... return ContentService .createTextOutput(callback+'('+ JSON.stringify({"result":"success", "row": nextRow})+')') .setMimeType(ContentService.MimeType.JAVASCRIPT);之前，您应确保首先设置actionBar，如下所示：

getActionBar()

setDisplayHomeAsUpEnabled（bool）使用FragmentActivity的null对象引用

2 个答案: