Question

我正在进行初学者Android任务（一个应该购买Car Ferry门票并计算门票费用的App），我遇到了让App在模拟器中运行的问题。我已经有了一个在模拟器中运行的示例程序，但我无法弄清楚这个问题是什么。从侧面说明我正在使用Mac，如果这意味着什么，我正在运行Eclipse。这是MainActivity.java代码：

package net.androidbootcamp.carferryfare;

import java.text.DecimalFormat;

import android.support.v7.app.ActionBarActivity;
import android.os.Bundle;
import android.view.Menu;
import android.view.MenuItem;
import android.view.View;
import android.widget.Button;
import android.widget.EditText;
import android.widget.Spinner;
import android.widget.TextView;
import android.view.View.OnClickListener;



public class MainActivity extends ActionBarActivity 
{
int costPerTicket = 18;
int numberOfTickets = 0;
int totalCost = 0;
String ferryChoice = "";
@Override
protected void onCreate(Bundle savedInstanceState) 
{
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);
    final EditText tickets=( EditText)findViewById(R.id.txtTickets);
    final Spinner group=(Spinner)findViewById(R.id.txtGroup);
    Button cost = (Button)findViewById(R.id.btnCost);
    final TextView result = ((TextView)findViewById(R.id.txtResult));   
    cost.setOnClickListener( new OnClickListener()
    {



        @Override

        public void onClick(View v) 
        {
            // TODO Auto-generated method stub
            numberOfTickets =  Integer.parseInt(tickets.getText().toString());
            totalCost = costPerTicket * numberOfTickets;
            DecimalFormat currency = new DecimalFormat("$###,###");
            ferryChoice = group.getSelectedItem().toString();
            result.setText("Total Cost for " + ferryChoice + " is " +       currency.format(totalCost));
        }

        });

}


@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;
}

@Override
public boolean onOptionsItemSelected(MenuItem item) {
    // Handle action bar item clicks here. The action bar will
    // automatically handle clicks on the Home/Up button, so long
    // as you specify a parent activity in AndroidManifest.xml.
    int id = item.getItemId();
    if (id == R.id.action_settings) {
        return true;
    }
    return super.onOptionsItemSelected(item);
}
}

以下是显示的LogCat数据：

09-29 18:18:56.049: D/AndroidRuntime(2033): Shutting down VM
09-29 18:18:56.099: W/dalvikvm(2033): threadid=1: thread exiting with uncaught exception        (group=0xb0cd7b20)
09-29 18:18:56.159: E/AndroidRuntime(2033): FATAL EXCEPTION: main
09-29 18:18:56.159: E/AndroidRuntime(2033): Process: net.androidbootcamp.carferryfare, PID:    2033
09-29 18:18:56.159: E/AndroidRuntime(2033): java.lang.RuntimeException: Unable to start    activity     ComponentInfo{net.androidbootcamp.carferryfare/net.androidbootcamp.carferryfare.MainActivity}:    java.lang.IllegalStateException: You need to use a Theme.AppCompat theme (or descendant) with   this activity.
09-29 18:18:56.159: E/AndroidRuntime(2033):     at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2195)
09-29 18:18:56.159: E/AndroidRuntime(2033):     at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2245)
09-29 18:18:56.159: E/AndroidRuntime(2033):     at android.app.ActivityThread.access$800(ActivityThread.java:135)
09-29 18:18:56.159: E/AndroidRuntime(2033):     at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1196)
09-29 18:18:56.159: E/AndroidRuntime(2033):     at android.os.Handler.dispatchMessage(Handler.java:102)
09-29 18:18:56.159: E/AndroidRuntime(2033):     at android.os.Looper.loop(Looper.java:136)
09-29 18:18:56.159: E/AndroidRuntime(2033):     at android.app.ActivityThread.main(ActivityThread.java:5017)
09-29 18:18:56.159: E/AndroidRuntime(2033):     at java.lang.reflect.Method.invokeNative(Native Method)
09-29 18:18:56.159: E/AndroidRuntime(2033):     at java.lang.reflect.Method.invoke(Method.java:515)
09-29 18:18:56.159: E/AndroidRuntime(2033):     at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:779)
09-29 18:18:56.159: E/AndroidRuntime(2033):     at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:595)
09-29 18:18:56.159: E/AndroidRuntime(2033):     at dalvik.system.NativeStart.main(Native Method)
09-29 18:18:56.159: E/AndroidRuntime(2033): Caused by: java.lang.IllegalStateException: You need to use a Theme.AppCompat theme (or descendant) with this activity.
09-29 18:18:56.159: E/AndroidRuntime(2033):     at android.support.v7.app.ActionBarActivityDelegate.onCreate(ActionBarActivityDelegate.java:110)
09-29 18:18:56.159: E/AndroidRuntime(2033):     at android.support.v7.app.ActionBarActivityDelegateICS.onCreate(ActionBarActivityDelegateICS.java:57)
09-29 18:18:56.159: E/AndroidRuntime(2033):     at android.support.v7.app.ActionBarActivity.onCreate(ActionBarActivity.java:99)
09-29 18:18:56.159: E/AndroidRuntime(2033):     at net.androidbootcamp.carferryfare.MainActivity.onCreate(MainActivity.java:27)
09-29 18:18:56.159: E/AndroidRuntime(2033):     at android.app.Activity.performCreate(Activity.java:5231)
09-29 18:18:56.159: E/AndroidRuntime(2033):     at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1087)
09-29 18:18:56.159: E/AndroidRuntime(2033):     at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2159)
09-29 18:18:56.159: E/AndroidRuntime(2033):     ... 11 more
09-29 18:19:04.359: I/Process(2033): Sending signal. PID: 2033 SIG: 9

Answer 1

好的，我很清楚我需要在MainActivity.java部分中包含：import android.app.Activity;作为导入，这就是代码无效的原因。谢谢panini，希望这可以帮助其他遇到同样问题的人。

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