java - Android 和 Java 无法解析为类型

Question

尝试调用 Android 中另一个类中的方法。我今天才刚刚开始 Android 开发，所以这对我来说是全新的。我想做的就是通过单击按钮来运行我的代码。

但是，在我的按钮代码中，我遇到了一个问题，IDE 告诉我无法将其解析为类型。谁能帮我解决这个问题？

然后是我的主要 Activity 课。这是错误所在:

import android.app.Activity;
import android.content.Intent;
import android.os.Bundle;
import android.view.Menu;
import android.view.MotionEvent;
import android.view.View;
import android.view.View.OnTouchListener;
import android.widget.Button;

public class MainActivity extends Activity {
Button aButton;

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);

    addListeners();



}

@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;
}

private void addListeners() {
      Button btnCallMethod = (Button) this.findViewById(R.id.btnCallMethod);

      // CALL METHOD BUTTON
      btnCallMethod.setOnTouchListener(new OnTouchListener() {

         @Override
         public boolean onTouch(View v, MotionEvent event) {
         if (event.getAction() == MotionEvent.ACTION_UP) {
              // error is on this line below
               Intent intent = new Intent(getApplicationContext(), DeviceScanActivity.class);
               startActivity(intent); // start the DeciveScanActivity
             }
             return false;
           }
         });
        }
}

更新我的 DeviceScanActivity 类的代码:

import android.annotation.TargetApi;
import android.app.ListActivity;
import android.bluetooth.BluetoothAdapter;
import android.bluetooth.BluetoothDevice;
import android.bluetooth.BluetoothManager;
import android.content.Context;
import android.os.Bundle;
import android.os.Handler;
import android.widget.ArrayAdapter;


@TargetApi(18)
public class DeviceScanActivity extends ListActivity {

    private Handler mHandler;

    // Stops scanning after 10 seconds.
    private static final long SCAN_PERIOD = 10000;

    private ArrayAdapter<Object> list;
    protected void OnCreate(Bundle savedInstanceState){
        super.onCreate(savedInstanceState);


        Bundle b = getIntent().getExtras();
        int key = b.getInt("yourKey");

        switch(key)
        {
           case 1: // call method here

            list = new ArrayAdapter<Object>(getApplicationContext(), 
                    android.R.layout.simple_list_item_1);
            setListAdapter(list);
            scanLeDevice(true);
        }

    }

    @TargetApi(18)
    public void scanLeDevice(final boolean enable) {
        list.add("Scanning...");
        final BluetoothAdapter adapter = getBluetoothAdapter();
        if (enable) {
            // Stops scanning after a pre-defined scan period.
            mHandler.postDelayed(new Runnable() {
                @Override
                public void run() {
                    // mBluetoothAdapter.stopLeScan(mLeScanCallback);
                    adapter.stopLeScan(callback);
                    list.clear();
                }
            }, SCAN_PERIOD);

            adapter.startLeScan(callback);
        } else {
            adapter.stopLeScan(callback);
        }

    }
    @TargetApi(18)
    private BluetoothAdapter getBluetoothAdapter()
    {
        BluetoothManager manager = (BluetoothManager) getSystemService(Context.BLUETOOTH_SERVICE);
        return manager.getAdapter();
    }
    private final BluetoothAdapter.LeScanCallback callback = new BluetoothAdapter.LeScanCallback() 
    {

        @Override
        public void onLeScan(final BluetoothDevice device, int rssi, byte[] scanRecord) {
            // TODO Auto-generated method stub

            {
                list.add("found: " + device);
                runOnUiThread(new Runnable(){
                    @Override
                    public void run()
                    {
                        list.add(device);
                        list.notifyDataSetChanged();
                    }
                });
        }
    }
    };

}

还有我的 list Xml，我认为它对于 Android 很重要:

<?xml version="1.0" encoding="utf-8"?>

<application
    android:allowBackup="true"
    android:icon="@drawable/ic_launcher"
    android:label="@string/app_name"
    android:theme="@style/AppTheme" >
    <activity
        android:name="com.example.bletest.MainActivity"
        android:label="@string/app_name" >
        <intent-filter>
            <action android:name="android.intent.action.MAIN" />

            <category android:name="android.intent.category.LAUNCHER" />
        </intent-filter>
    </activity>
</application>

Answer 1

您需要确保在添加新类(在本例中为DeviceScanActivity)时，将其添加到正确的包中。

当您右键单击项目并单击“新建 -> 类”时，它不会为您填充包名称。有两种方法可以确保将其添加到正确的包中:

• 不要右键单击项目来添加类，而是右键单击包。

  • Your projects packages can be found in either the Package Explorer or Project explorer by expanding the src folder. the next layer down should be packages.

• 您可以手动将包名称添加到新建 Java 类 对话框中。 “包”应该位于顶部附近。

注意，这假设您使用的是 Eclipse IDE/ADT。如果没有，具体步骤可能会有所不同。

---

其次，您需要将任何新的 Activity 类添加到 list 中。如果不是，您将不会收到 Can't be returned to a type 错误，但您会收到运行时错误，因此请继续修复它。至少，您需要类似的东西:

<activity
    android:name="com.example.bletest.DeviceScanActivity"
</activity>