mCamera不能被解析为一个变量（Android的是，Eclipse）

问题描述

我很新的Andr​​oid开发。我下面谷歌的Andr​​oid类和我在Eclipse中收到一条错误此code：

I am very new to Android development. I am following Google's Android "classes" and am receiving an error for this code in Eclipse:

package com.feistie.myfirstapp;

import android.app.ActionBar;
import android.app.Activity;
import android.content.Intent;
import android.os.Build;
import android.os.Bundle;
import android.view.Menu;
import android.view.View;
import android.widget.EditText;
import android.widget.TextView;

public class MainActivity extends Activity {

    public final static String EXTRA_MESSAGE = "com.example.myfirstapp.MESSAGE";

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

        // Initialize member TextView so we can manipulate it later
        mTextView = (TextView) findViewById(R.id.text_message);

        if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.HONEYCOMB) {
            // For the main activity, make sure the app icon in the action bar
            //does not behave as a buutton
            ActionBar actionBar = getActionBar();
            actionBar.setHomeButtonEnabled(false);
        }
    }

    @Override
    public void onDestroy() {
        super.onDestroy();  // Always call the superclass

        // Stop method tracing that the activity started during onCreate()
        android.os.Debug.stopMethodTracing();
    }

    @Override
    public void onPause() {
        super.onPause();  // Always call the superclass method first

        // Release the Camera because we don't need it when paused
        // and other activities might need to use it.
        if (mCamera != null) {
            mCamera.release();
            mCamera = null;
        }
    }

    @Override
    public boolean onCreateOptionsMenu(Menu menu) {
        getMenuInflater().inflate(R.menu.activity_main, menu);
        return true;
    }

    /** Called when the user clicks the Send button */
    public void sendMessage (View view) {
        // Do Something in response to button
        Intent intent = new Intent(this, DisplayMessageActivity.class);
        EditText editText = (EditText) findViewById(R.id.edit_message);
        String message = editText.getText().toString();
        intent.putExtra(EXTRA_MESSAGE, message);
        startActivity(intent);
    }
}

有一个错误的这些行：

There is an error for each of these lines:

if (mCamera != null) {
                mCamera.release();
                mCamera = null;
            }

有第一和第三行中的错误表示，mCamera不能解析为一个变量。第二行的错误只是说mCamera解决不了的。

The error for the first and third lines says "mCamera cannot be resolved to a variable." The error for the second line just says "mCamera cannot be resolved."

如果您需要了解更多信息，请让我知道。

If you need more information please let me know.

谢谢！

推荐答案

您需要声明 mCamera 之前，你可以参考吧：

You need to declare mCamera before you can reference it:

public class MainActivity extends Activity {
    Camera mCamera;

然后你需要初始化它，大概在onResume（）

And then you need to initialize it, probably in onResume()

@Override
protected void onResume() {
    super.onResume();
    mCamera = Camera.open()
}

请确保你补充说，你表现出适当的权限：

Make sure you added the appropriate permission that you manifest:

<uses-permission android:name="android.permission.CAMERA" />

添加

您需要在您尝试使用它在Java中declare_every_变量。我没有看到你声明 mTextView 无论是。

You need to declare_every_ variable before you try use it in Java. I don't see where you declare mTextView either.

public class MainActivity extends Activity {
    Camera mCamera;
    TextView mTextView;

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