java - 从包名称获取应用程序名称

我正在尝试插入应用程序的名称作为首选项的摘要。我编写了这段代码，但是它不起作用，因为在运行此行时，应用程序崩溃并显示NullPointerException

name.setSummary(Pm.getApplicationLabel(nameApp));

该代码是

    value2 = getIntent().getStringExtra("ApplicationName");

    PackageManager Pm = getPackageManager();

    ApplicationInfo nameApp = Pm.getApplicationInfo(value2, 0);

    name.setSummary(Pm.getApplicationLabel(nameApp));

Value2是一个变量的名称，该变量采用了上一个Activity产生的包的名称，在正确地传递和恢复包名称的意义上，此步骤效果很好

最佳答案

尝试这个..

    PackageManager packageManager=this.getPackageManager();
    List<ApplicationInfo applist=packageManager.getInstalledApplications(0);


    Iterator<ApplicationInfo> it=applist.iterator();
    while(it.hasNext()){
        ApplicationInfo pk=(ApplicationInfo)it.next();

        String appname = packageManager.getApplicationLabel(pk).toString();
        System.out.println("Application name : "+appname);
    }

或特定的包装名称

final PackageManager pm = getApplicationContext().getPackageManager();
ApplicationInfo ai;
try {
    ai = pm.getApplicationInfo(PackageName, 0);
} catch (final NameNotFoundException e) {
    ai = null;
}
final String applicationName = (String) (ai != null ? pm.getApplicationLabel(ai) : "(unknown)");
System.out.println("Application name : "+applicationName);