Question

我的项目运行良好，直到我为我的微调器声明了一个onItemSelctedListener。现在我的项目没有运行..日志猫显示以下错误...

03-03 01:59:08.465: E/AndroidRuntime(1401):
     FATAL EXCEPTION: main
     Process: com.example.testqstn, PID: 1401
     java.lang.RuntimeException: Unable to instantiate activity
       ComponentInfo{com.example.testqstn/com.example.testqstn.MainActivity}: 
       java.lang.IllegalStateException: System services not available to Activities
       before onCreate()
     at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2121)
     at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2245)
     at android.app.ActivityThread.access$800(ActivityThread.java:135)
     at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1196)
     at android.os.Handler.dispatchMessage(Handler.java:102)
     at android.os.Looper.loop(Looper.java:136)
     at android.app.ActivityThread.main(ActivityThread.java:5017)
     at java.lang.reflect.Method.invokeNative(Native Method)
     at java.lang.reflect.Method.invoke(Method.java:515)
     at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:779)
     at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:595)
     at dalvik.system.NativeStart.main(Native Method)
     Caused by: java.lang.IllegalStateException: System services not available to Activities before onCreate()
     at android.app.Activity.getSystemService(Activity.java:4532)
     at android.widget.ArrayAdapter.init(ArrayAdapter.java:310)
     at android.widget.ArrayAdapter.<init>(ArrayAdapter.java:153)
     at com.example.testqstn.MainActivity.<init>(MainActivity.java:39)
     at java.lang.Class.newInstanceImpl(Native Method)
     at java.lang.Class.newInstance(Class.java:1208)
     at android.app.Instrumentation.newActivity(Instrumentation.java:1061)
     at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2112)

现在要注意的要点是

1）主要活动方法根本没有实现..甚至没有super.onCreate

现在这是我输入的代码..但由于它没有实现，id odnt知道abt它的相关性..

protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.main);
    main(); 
}

public void main()
{
    TextView textyear,textsubject,textschema;
    Typeface typeface = Typeface.createFromAsset(getAssets(), "fonts/Roboto/Roboto-Light.ttf");
    textyear = (TextView)findViewById(R.id.textyear);
    textsubject = (TextView)findViewById(R.id.textsubject);
    textschema = (TextView)findViewById(R.id.textscheme);

    textyear.setTypeface(typeface);
    textsubject.setTypeface(typeface);
    textschema.setTypeface(typeface);

    year = (Spinner)findViewById(R.id.spinyear);
    subject = (Spinner)findViewById(R.id.spinsub);
    scheme = (Spinner)findViewById(R.id.spinscheme);
    schemetxt = scheme.toString();
    buttonSound = MediaPlayer.create(MainActivity.this,R.raw.sound );
    btn=(Button)findViewById(R.id.button);
    btn.setBackgroundResource(R.drawable.selector);
    // set dynamic value change

    scheme.setOnItemSelectedListener(new OnItemSelectedListener() {

        @Override
        public void onItemSelected(AdapterView<?> arg0, View arg1,
                int arg2, long arg3) {
            // TODO Auto-generated method stub
            listYear(schemetxt);

        }

        @Override
        public void onNothingSelected(AdapterView<?> arg0) {
            // TODO Auto-generated method stub

        }
    });
    btn.setOnClickListener(new View.OnClickListener() {
        public void onClick(View v)
        {
            pdfSelection(v);
        }
       });


}
@Override
public boolean onCreateOptionsMenu(Menu menu) {
    // Inflate the menu; this adds items to the action bar if it is present.
    getMenuInflater().inflate(R.menu.main, menu);
    return true;
}

这是列表视图功能

    myAdapter1 = new ArrayAdapter<String>(this, android.R.layout.simple_spinner_item, listYear);
    myAdapter1.setDropDownViewResource(android.R.layout.simple_spinner_dropdown_item);
    year.setAdapter(myAdapter1);

那么错误是什么？提前谢谢..

这是代码b4我的oncreate函数

   Button btn;  
Spinner year , subject , scheme;
String yeartxt = null;
String subtxt = null;
String schemetxt = null;
List<String> listYear;
ArrayAdapter<String> myAdapter1 = new ArrayAdapter<String>(this, android.R.layout.simple_spinner_item, listYear);
MediaPlayer buttonSound;

Answer 1

关键部分在这里：

Caused by: java.lang.IllegalStateException: System services not available to Activities before onCreate()

进一步向下走栈：

at android.widget.ArrayAdapter.<init>(ArrayAdapter.java:153)
at com.example.testqstn.MainActivity.<init>(MainActivity.java:39)

因此，您要将ArrayAdapter初始化为MainActivity的成员变量，特别是MainActivity.java的第39行。你不能这样做。您可以将其声明为成员变量，但在new或更高版本中对其进行初始化（onCreate()}。

从更新的问题代码中，替换声明+初始化

ArrayAdapter<String> myAdapter1 = new ArrayAdapter<String>(this, android.R.layout.simple_spinner_item, listYear);

只有声明

ArrayAdapter<String> myAdapter1;

并移动初始化

myAdapter1 = new ArrayAdapter<String>(this, android.R.layout.simple_spinner_item, listYear);

介于onCreate()和首次使用myAdapter1之间的某个位置。

Answer 2

引起：java.lang.IllegalStateException：系统服务没有在onCreate（）
之前可用于活动

创建活动后可以使用上下文。

http://developer.android.com/reference/android/content/Context.html

编辑：

ArrayAdapter<String> myAdapter1;
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
// make sure listYear is populated before this
myAdapter1 = new ArrayAdapter<String>(this, android.R.layout.simple_spinner_item, listYear);

同时重命名listYear(schemetxt);或List<String> listYear有助于实现可读性

Logcat乱码...微调器，onItemSelectedListener

2 个答案:

Logcat乱码...微调器，​​onItemSelectedListener

2 个答案:

Logcat乱码...微调器，onItemSelectedListener