什么是错的 - 河内的塔

时间:2011-05-06 19:45:29

标签: android

可以解释一下为什么当我在android模拟器上部署它时这个代码不能正常工作

public class towers extends Activity {

    /** Called when the activity is first created. */
    private EditText text;
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);
        text = (EditText) findViewById(R.id.editText1);   
    }

    static int moves = 0;
    static int totalDisks = 0;

    public void myClickHandler(View view) throws java.io.IOException {
        char fromPole = 'A';
        char withPole = 'B';
        char toPole = 'C';

        switch (view.getId()) {
            case R.id.editText1:

                if (text.getText().length() == 0) {
                    Toast.makeText(this, "Please enter number of disks",
                            Toast.LENGTH_LONG).show();
                    return;
                }
                float disks = Float.parseFloat(text.getText().toString());
                FileOutputStream fos = new FileOutputStream("TowersOfHanoiSolution.txt");
                PrintStream ps = new PrintStream(fos);
                solveHanoi(disks, fromPole, toPole, withPole, ps);
                ps.close();
                System.out.println();
                text.setText("\nAmount of moves: " + moves + "\n");
        }

    }

    static void solveHanoi(float disks, char start, char end, char intermediate, PrintStream ps) {
        if (disks >= 1) {
            solveHanoi(disks-1, start, intermediate, end, ps);
            moveDisk(start, end, ps);
            solveHanoi(disks-1, intermediate, end, start, ps);
        }
    }

    static void moveDisk(char fromPole, char toPole, PrintStream ps) {
        moves++;

        if(totalDisks <= 10){
            System.out.print("Move from " + fromPole + " to " + toPole + ". ");
            ps.print("Move from " + fromPole + " to " + toPole + ". ");
            if (moves%4 == 0){
                System.out.println();
                ps.println();
            }
        }
        else {
            ps.print("Move from " + fromPole + " to " + toPole + ". ");
            if (moves%4 == 0){
                ps.println();
            }
        }
    }
}

1 个答案:

答案 0 :(得分:1)

我将假设您的布局在myClickHandler的{​​{1}}属性中声明android:onClick,但最好包含您的布局以防止人们猜测。例如,如果editText1处理程序连接不正确或根本没有连接,您将收到另一个例外,或者什么都不会发生。

但我会假设该方法被正确调用。您尝试创建文件而未指定路径,因此它尝试打开onClick并收到/TowersOfHanoiSolution.txt,其原因是“只读文件系统”:

FileNotFoundException

您使用的是Eclipse吗?如果使用Eclipse进行调试,则可以在logcat窗口中获取类似上述的堆栈跟踪,并且还可以暂停执行以让您检查应用程序的状态。但是,只需观察Caused by: java.io.FileNotFoundException: /TowersOfHanoiSolution.txt (Read-only file system) at org.apache.harmony.luni.platform.OSFileSystem.open(Native Method) at dalvik.system.BlockGuard$WrappedFileSystem.open(BlockGuard.java:232) at java.io.FileOutputStream.<init>(FileOutputStream.java:94) at java.io.FileOutputStream.<init>(FileOutputStream.java:165) at java.io.FileOutputStream.<init>(FileOutputStream.java:144) at com.example.towers.towers.myClickHandler(towers.java:49) ... 14 more 或Eclipse的LogCat窗口就可以更简单地查看异常是什么;关键信息是引用代码的第一个行号。

请注意,这不是主要的例外;主要的例外是框架抱怨adb logcat调用失败。同样,这就是为什么在调试器中暂停执行可能过于复杂,并且只需读取logcat以查看所有异常是什么就更容易了。

无论如何:您无法在Android上onClick创建文件;因为这是工作目录,你需要指定完整路径(我假设为SD卡)。像这样:

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