我在从另一个类调用的方法中获取视图以正常运行时遇到了一些困难。
我的应用程序包含一个主要活动(称为“覆盖”)中的体验栏,该体验栏使用进度条跟踪用户的进度。我想做的是在另一个类中有一个单独的方法来处理与体验栏相关的任何代码。
我已经为该类创建了一个实例,并且该方法已正确调用,但是某些与android / view相关的片段会导致麻烦。System.out.println将在调试器中显示文本,但是不会使用Toast和其他视图。这是两个类文件和相关的错误。
public class OverlayActivity extends AppCompatActivity
implements NavigationView.OnNavigationItemSelectedListener {
NavigationView navigationView = null;
Toolbar toolbar = null;
int level = 0;
int addXP = 110;
ProgressBar experienceBar;
Button buttonXP;
TextView experienceLevel;
ExperienceManager exp;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_overlay);
//Set the Overlay Fragment
OverlayFragment fragment = new OverlayFragment();
android.support.v4.app.FragmentTransaction fragmentTransaction =
getSupportFragmentManager().beginTransaction();
fragmentTransaction.replace(R.id.fragment_container, fragment);
fragmentTransaction.commit();
toolbar = (Toolbar) findViewById(R.id.toolbar);
setSupportActionBar(toolbar);
FloatingActionButton fab = (FloatingActionButton) findViewById(R.id.fab);
fab.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View view) {
Snackbar.make(view, "Hay! Don't touch me!", Snackbar.LENGTH_LONG)
.setAction("Action", null).show();
}
});
DrawerLayout drawer = (DrawerLayout) findViewById(R.id.drawer_layout);
ActionBarDrawerToggle toggle = new ActionBarDrawerToggle(
this, drawer, toolbar, R.string.navigation_drawer_open, R.string.navigation_drawer_close);
drawer.setDrawerListener(toggle);
toggle.syncState();
navigationView = (NavigationView) findViewById(R.id.nav_view);
navigationView.setNavigationItemSelectedListener(this);
experienceBar = (ProgressBar) findViewById(R.id.experienceBar);
experienceBar.setProgress(12);
experienceLevel = (TextView) findViewById(R.id.ds_appBar_level);
buttonXP = (Button) findViewById(R.id.buttonXP);
buttonXP.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View View) {
exp = new ExperienceManager();
exp.addExperience(level, addXP);
}
});
}
public class ExperienceManager extends AppCompatActivity {
ProgressBar experienceBar;
public int addExperience(int level, int addXP) {
experienceBar = (ProgressBar) findViewById(R.id.experienceBar);
int addLevel = 0;
while (addXP >= experienceBar.getMax()) {
addXP -= experienceBar.getMax();
addLevel += 1;
}
if (addXP >= experienceBar.getMax()-experienceBar.getProgress()) {
experienceBar.setProgress(experienceBar.getProgress() + addXP - experienceBar.getMax());
addLevel += 1;
} else {
experienceBar.setProgress(experienceBar.getProgress() + addXP);
}
if (addLevel >= 1) {
level += addLevel;
Toast toast = Toast.makeText(getBaseContext(), "Level up!", Toast.LENGTH_SHORT);
toast.show();
//experienceLevel.setText("Level " + level);
}
return level;
}
E/AndroidRuntime: FATAL EXCEPTION: main
Process: com.teamcirelios.deepstone, PID: 4138
java.lang.NullPointerException: Attempt to invoke virtual method 'android.view.Window$Callback android.view.Window.getCallback()' on a null object reference
at android.support.v7.app.AppCompatDelegateImplBase.<init>(AppCompatDelegateImplBase.java:116)
at android.support.v7.app.AppCompatDelegateImplV9.<init>(AppCompatDelegateImplV9.java:147)
at android.support.v7.app.AppCompatDelegateImplV11.<init>(AppCompatDelegateImplV11.java:27)
at android.support.v7.app.AppCompatDelegateImplV14.<init>(AppCompatDelegateImplV14.java:50)
at android.support.v7.app.AppCompatDelegateImplV23.<init>(AppCompatDelegateImplV23.java:29)
at android.support.v7.app.AppCompatDelegate.create(AppCompatDelegate.java:199)
at android.support.v7.app.AppCompatDelegate.create(AppCompatDelegate.java:181)
at android.support.v7.app.AppCompatActivity.getDelegate(AppCompatActivity.java:521)
at android.support.v7.app.AppCompatActivity.findViewById(AppCompatActivity.java:190)
at com.teamcirelios.deepstone.ExperienceManager.addExperience(ExperienceManager.java:15)
at com.teamcirelios.deepstone.OverlayActivity$2.onClick(OverlayActivity.java:77)
at android.view.View.performClick(View.java:5697)
at android.widget.TextView.performClick(TextView.java:10826)
at android.view.View$PerformClick.run(View.java:22526)
at android.os.Handler.handleCallback(Handler.java:739)
at android.os.Handler.dispatchMessage(Handler.java:95)
at android.os.Looper.loop(Looper.java:158)
at android.app.ActivityThread.main(ActivityThread.java:7225)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1230)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1120)
同样,尝试在片段中注册按钮单击时,也会产生类似的错误。体验栏本身以叠加活动显示,但是要使应用程序按预期工作,它需要从片段中的按钮(或更准确地说是复选框)接收输入以调用该类。
我能看到的唯一解决方案是采用experienceBar.getMax()和类似的东西,并将它们作为参数包括在内。但是,我需要同时返回级别和当前xp,据我所知这是不可能的。
总的来说,我有三个主要问题。
谢谢!
首先,您的实用程序类(即体验管理器)不应扩展AppCompatActivity ...您的实用程序类不是活动!PS,您无法在Experience Manager中找到ViewById和progressBar,因为该ProgressBar不是ExperienceManager活动的一部分,而是OverlayActivity的一部分。
如果您希望创建一个静态实用程序方法来增加经验并对其进行管理,则应以这种方式编写代码。
public class ExperienceManager{
public static int addExperience(ProgressBar experienceBar, int level, int addXP){
int addLevel = 0;
while (addXP >= experienceBar.getMax()) {
addXP -= experienceBar.getMax();
addLevel += 1;
}
if (addXP >= experienceBar.getMax()-experienceBar.getProgress()) {
experienceBar.setProgress(experienceBar.getProgress() + addXP - experienceBar.getMax());
addLevel += 1;
} else {
experienceBar.setProgress(experienceBar.getProgress() + addXP);
}
if (addLevel >= 1) {
level += addLevel;
Toast toast = Toast.makeText(getBaseContext(), "Level up!", Toast.LENGTH_SHORT);
toast.show();
//experienceLevel.setText("Level " + level);
}
return level;
}
}
您可以通过以下方式调用此方法:
buttonXP.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View View) {
// Calling the static utility method over here...
ExperienceManager.addExperience(experienceBar, level, addXP);
}
});
那就是你需要做的:)
我建议您在尝试Android之前先熟悉Java设计模式和最佳编程实践。
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