Android 快速入門導覽課程

本指南說明如何設定簡單的 Android 應用程式,以便向 YouTube Data API 提出要求。

必要條件

如要執行這個快速入門導覽課程,您需要:

本快速入門導覽課程假設您使用的是 Android Studio IDE (而非獨立的 SDK 工具),且能輕鬆在 Studio 專案中尋找、建立及編輯檔案。

步驟 1:取得 SHA1 指紋

在終端機中,執行下方的 Keytool 公用程式指令,取得您將用來啟用 API 的 SHA1 指紋。

keytool -exportcert -alias androiddebugkey -keystore ~/.android/debug.keystore -list -v

系統要求您提供 KeyStore 密碼時,請輸入「android」。

Keytool 會將指紋列印至殼層。例如:

$ keytool -exportcert -alias androiddebugkey -keystore ~/.android/debug.keystore -list -v
Enter keystore password: Type "android" if using debug.keystore
Alias name: androiddebugkey
Creation date: Dec 4, 2014
Entry type: PrivateKeyEntry
Certificate chain length: 1
Certificate[1]:
Owner: CN=Android Debug, O=Android, C=US
Issuer: CN=Android Debug, O=Android, C=US
Serial number: 503bd581
Valid from: Mon Aug 27 13:16:01 PDT 2012 until: Wed Aug 20 13:16:01 PDT 2042
Certificate fingerprints:
   MD5:  1B:2B:2D:37:E1:CE:06:8B:A0:F0:73:05:3C:A3:63:DD
   SHA1: D8:AA:43:97:59:EE:C5:95:26:6A:07:EE:1C:37:8E:F4:F0:C8:05:C8
   SHA256: F3:6F:98:51:9A:DF:C3:15:4E:48:4B:0F:91:E3:3C:6A:A0:97:DC:0A:3F:B2:D2:E1:FE:23:57:F5:EB:AC:13:30
   Signature algorithm name: SHA1withRSA
   Version: 3

複製在上述範例中醒目顯示的 SHA1 指紋。

步驟 2:啟用 YouTube Data API

  1. 使用這個精靈在 Google Developers Console 中建立或選取專案,並自動啟用這個 API。依序點選「繼續」和「前往憑證」

  2. 在「建立憑證」頁面上,按一下「取消」按鈕。

  3. 選取頁面頂端的「OAuth 同意畫面」分頁標籤。選取「Email address」(電子郵件地址),輸入「Product name」(產品名稱) (如果尚未設定),然後按一下「Save」(儲存) 按鈕。

  4. 選取「憑證」分頁標籤,按一下「建立憑證」按鈕,然後選取「OAuth 用戶端 ID」

  5. 選取「Android」應用程式類型。
  6. 將步驟 1 中的 SHA1 指紋複製到「簽署憑證指紋」欄位。
  7. 「Package name」(套件名稱) 欄位中輸入 com.example.quickstart
  8. 按一下「Create」(建立) 按鈕。

步驟 3:建立新的 Android 專案

  1. 開啟 Android Studio,然後開啟新的 Android Studio 專案。
  2. 在「New Project」畫面中,將應用程式命名為「quickstart」。
  3. 將「Company Domain」設為「example.com」,並確認自動產生的套件名稱與您在步驟 2 中在開發人員控制台輸入的名稱相符。按一下「Next」
  4. 在「Target Android Devices」畫面中,勾選「Phone and Tablet」核取方塊,然後選擇「API 14: Android 4.0 (IceCreamSandwich)」的「Minimum SDK」。而不勾選其他核取方塊。按一下「Next」
  5. 在「Add an activity to Mobile」畫面中,按一下「Add No Activity」
  6. 按一下「Finish」

此時,Android Studio 會建立並開啟專案。

步驟 4:準備專案

「專案」側欄會顯示 Android Studio 建立的預設專案檔案的可展開清單。在清單中展開 Gradle 指令碼清單,並開啟與「應用程式」模組 (而非專案) 相關聯的 build.gradle 檔案。

  1. 開啟應用程式 build.gradle 檔案,並將內容替換為以下內容:
  2. 在工具列中,依序選取「Tools」>「Android」>「Sync Project with Gradle Files」。藉此取得並提供專案所需的程式庫。
  3. 找出並開啟預設的 src/main/AndroidManifest.xml 檔案。在「Project」側欄中,這個檔案以巢狀結構列於 app 下方,然後在 manifests 下方。將檔案內容替換成下列程式碼:
    <?xml version="1.0" encoding="utf-8"?>
    <manifest xmlns:android="http://schemas.android.com/apk/res/android"
        package="com.example.quickstart">
    
        <uses-permission android:name="android.permission.INTERNET" />
        <uses-permission android:name="android.permission.ACCESS_NETWORK_STATE" />
        <uses-permission android:name="android.permission.GET_ACCOUNTS" />
    
        <application
            android:allowBackup="true"
            android:icon="@mipmap/ic_launcher"
            android:label="YouTube Data API Android Quickstart"
            android:theme="@style/AppTheme" >
            <activity
                android:name=".MainActivity"
                android:label="YouTube Data API Android Quickstart" >
                <intent-filter>
                    <action android:name="android.intent.action.MAIN" />
                    <category android:name="android.intent.category.LAUNCHER" />
                </intent-filter>
            </activity>
    
        </application>
    </manifest>

步驟 5:設定範例

建立新的 Java 類別。方法是先在「Project」側欄中選取 java 資料夾。這個資料夾會顯示在 app 個檔案群組中。按一下資料夾後,可以從選單列中依序選取「File」(檔案) >「New」(新增) >「Java Class」;您也可以在資料夾上按一下滑鼠右鍵,然後依序選取「New」(新增) >「Java Class」(Java 類別)。如果系統提示您選取目錄,請選擇 .../app/src/main/java

將類別命名為「MainActivity」,然後按一下「OK」。使用下列程式碼取代新檔案的內容。

package com.example.quickstart;

import com.google.android.gms.common.ConnectionResult;
import com.google.android.gms.common.GoogleApiAvailability;
import com.google.api.client.extensions.android.http.AndroidHttp;
import com.google.api.client.googleapis.extensions.android.gms.auth.GoogleAccountCredential;
import com.google.api.client.googleapis.extensions.android.gms.auth.GooglePlayServicesAvailabilityIOException;
import com.google.api.client.googleapis.extensions.android.gms.auth.UserRecoverableAuthIOException;

import com.google.api.client.http.HttpTransport;
import com.google.api.client.json.JsonFactory;
import com.google.api.client.json.jackson2.JacksonFactory;
import com.google.api.client.util.ExponentialBackOff;

import com.google.api.services.youtube.YouTubeScopes;

import com.google.api.services.youtube.model.*;

import android.Manifest;
import android.accounts.AccountManager;
import android.app.Activity;
import android.app.Dialog;
import android.app.ProgressDialog;
import android.content.Context;
import android.content.Intent;
import android.content.SharedPreferences;
import android.net.ConnectivityManager;
import android.net.NetworkInfo;
import android.os.AsyncTask;
import android.os.Bundle;
import android.support.annotation.NonNull;
import android.text.TextUtils;
import android.text.method.ScrollingMovementMethod;
import android.view.View;
import android.view.ViewGroup;
import android.widget.Button;
import android.widget.LinearLayout;
import android.widget.TextView;

import java.io.IOException;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.List;

import pub.devrel.easypermissions.AfterPermissionGranted;
import pub.devrel.easypermissions.EasyPermissions;

public class MainActivity extends Activity
    implements EasyPermissions.PermissionCallbacks {
    GoogleAccountCredential mCredential;
    private TextView mOutputText;
    private Button mCallApiButton;
    ProgressDialog mProgress;

    static final int REQUEST_ACCOUNT_PICKER = 1000;
    static final int REQUEST_AUTHORIZATION = 1001;
    static final int REQUEST_GOOGLE_PLAY_SERVICES = 1002;
    static final int REQUEST_PERMISSION_GET_ACCOUNTS = 1003;

    private static final String BUTTON_TEXT = "Call YouTube Data API";
    private static final String PREF_ACCOUNT_NAME = "accountName";
    private static final String[] SCOPES = { YouTubeScopes.YOUTUBE_READONLY };

    /**
     * Create the main activity.
     * @param savedInstanceState previously saved instance data.
     */
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        LinearLayout activityLayout = new LinearLayout(this);
        LinearLayout.LayoutParams lp = new LinearLayout.LayoutParams(
                LinearLayout.LayoutParams.MATCH_PARENT,
                LinearLayout.LayoutParams.MATCH_PARENT);
        activityLayout.setLayoutParams(lp);
        activityLayout.setOrientation(LinearLayout.VERTICAL);
        activityLayout.setPadding(16, 16, 16, 16);

        ViewGroup.LayoutParams tlp = new ViewGroup.LayoutParams(
                ViewGroup.LayoutParams.WRAP_CONTENT,
                ViewGroup.LayoutParams.WRAP_CONTENT);

        mCallApiButton = new Button(this);
        mCallApiButton.setText(BUTTON_TEXT);
        mCallApiButton.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                mCallApiButton.setEnabled(false);
                mOutputText.setText("");
                getResultsFromApi();
                mCallApiButton.setEnabled(true);
            }
        });
        activityLayout.addView(mCallApiButton);

        mOutputText = new TextView(this);
        mOutputText.setLayoutParams(tlp);
        mOutputText.setPadding(16, 16, 16, 16);
        mOutputText.setVerticalScrollBarEnabled(true);
        mOutputText.setMovementMethod(new ScrollingMovementMethod());
        mOutputText.setText(
                "Click the \'" + BUTTON_TEXT +"\' button to test the API.");
        activityLayout.addView(mOutputText);

        mProgress = new ProgressDialog(this);
        mProgress.setMessage("Calling YouTube Data API ...");

        setContentView(activityLayout);

        // Initialize credentials and service object.
        mCredential = GoogleAccountCredential.usingOAuth2(
                getApplicationContext(), Arrays.asList(SCOPES))
                .setBackOff(new ExponentialBackOff());
    }

    

    /**
     * Attempt to call the API, after verifying that all the preconditions are
     * satisfied. The preconditions are: Google Play Services installed, an
     * account was selected and the device currently has online access. If any
     * of the preconditions are not satisfied, the app will prompt the user as
     * appropriate.
     */
    private void getResultsFromApi() {
        if (! isGooglePlayServicesAvailable()) {
            acquireGooglePlayServices();
        } else if (mCredential.getSelectedAccountName() == null) {
            chooseAccount();
        } else if (! isDeviceOnline()) {
            mOutputText.setText("No network connection available.");
        } else {
            new MakeRequestTask(mCredential).execute();
        }
    }

    /**
     * Attempts to set the account used with the API credentials. If an account
     * name was previously saved it will use that one; otherwise an account
     * picker dialog will be shown to the user. Note that the setting the
     * account to use with the credentials object requires the app to have the
     * GET_ACCOUNTS permission, which is requested here if it is not already
     * present. The AfterPermissionGranted annotation indicates that this
     * function will be rerun automatically whenever the GET_ACCOUNTS permission
     * is granted.
     */
    @AfterPermissionGranted(REQUEST_PERMISSION_GET_ACCOUNTS)
    private void chooseAccount() {
        if (EasyPermissions.hasPermissions(
                this, Manifest.permission.GET_ACCOUNTS)) {
            String accountName = getPreferences(Context.MODE_PRIVATE)
                    .getString(PREF_ACCOUNT_NAME, null);
            if (accountName != null) {
                mCredential.setSelectedAccountName(accountName);
                getResultsFromApi();
            } else {
                // Start a dialog from which the user can choose an account
                startActivityForResult(
                        mCredential.newChooseAccountIntent(),
                        REQUEST_ACCOUNT_PICKER);
            }
        } else {
            // Request the GET_ACCOUNTS permission via a user dialog
            EasyPermissions.requestPermissions(
                    this,
                    "This app needs to access your Google account (via Contacts).",
                    REQUEST_PERMISSION_GET_ACCOUNTS,
                    Manifest.permission.GET_ACCOUNTS);
        }
    }

    /**
     * Called when an activity launched here (specifically, AccountPicker
     * and authorization) exits, giving you the requestCode you started it with,
     * the resultCode it returned, and any additional data from it.
     * @param requestCode code indicating which activity result is incoming.
     * @param resultCode code indicating the result of the incoming
     *     activity result.
     * @param data Intent (containing result data) returned by incoming
     *     activity result.
     */
    @Override
    protected void onActivityResult(
            int requestCode, int resultCode, Intent data) {
        super.onActivityResult(requestCode, resultCode, data);
        switch(requestCode) {
            case REQUEST_GOOGLE_PLAY_SERVICES:
                if (resultCode != RESULT_OK) {
                    mOutputText.setText(
                            "This app requires Google Play Services. Please install " +
                            "Google Play Services on your device and relaunch this app.");
                } else {
                    getResultsFromApi();
                }
                break;
            case REQUEST_ACCOUNT_PICKER:
                if (resultCode == RESULT_OK && data != null &&
                        data.getExtras() != null) {
                    String accountName =
                            data.getStringExtra(AccountManager.KEY_ACCOUNT_NAME);
                    if (accountName != null) {
                        SharedPreferences settings =
                                getPreferences(Context.MODE_PRIVATE);
                        SharedPreferences.Editor editor = settings.edit();
                        editor.putString(PREF_ACCOUNT_NAME, accountName);
                        editor.apply();
                        mCredential.setSelectedAccountName(accountName);
                        getResultsFromApi();
                    }
                }
                break;
            case REQUEST_AUTHORIZATION:
                if (resultCode == RESULT_OK) {
                    getResultsFromApi();
                }
                break;
        }
    }

    /**
     * Respond to requests for permissions at runtime for API 23 and above.
     * @param requestCode The request code passed in
     *     requestPermissions(android.app.Activity, String, int, String[])
     * @param permissions The requested permissions. Never null.
     * @param grantResults The grant results for the corresponding permissions
     *     which is either PERMISSION_GRANTED or PERMISSION_DENIED. Never null.
     */
    @Override
    public void onRequestPermissionsResult(int requestCode,
                                           @NonNull String[] permissions,
                                           @NonNull int[] grantResults) {
        super.onRequestPermissionsResult(requestCode, permissions, grantResults);
        EasyPermissions.onRequestPermissionsResult(
                requestCode, permissions, grantResults, this);
    }

    /**
     * Callback for when a permission is granted using the EasyPermissions
     * library.
     * @param requestCode The request code associated with the requested
     *         permission
     * @param list The requested permission list. Never null.
     */
    @Override
    public void onPermissionsGranted(int requestCode, List<String> list) {
        // Do nothing.
    }

    /**
     * Callback for when a permission is denied using the EasyPermissions
     * library.
     * @param requestCode The request code associated with the requested
     *         permission
     * @param list The requested permission list. Never null.
     */
    @Override
    public void onPermissionsDenied(int requestCode, List<String> list) {
        // Do nothing.
    }

    /**
     * Checks whether the device currently has a network connection.
     * @return true if the device has a network connection, false otherwise.
     */
    private boolean isDeviceOnline() {
        ConnectivityManager connMgr =
                (ConnectivityManager) getSystemService(Context.CONNECTIVITY_SERVICE);
        NetworkInfo networkInfo = connMgr.getActiveNetworkInfo();
        return (networkInfo != null && networkInfo.isConnected());
    }

    /**
     * Check that Google Play services APK is installed and up to date.
     * @return true if Google Play Services is available and up to
     *     date on this device; false otherwise.
     */
    private boolean isGooglePlayServicesAvailable() {
        GoogleApiAvailability apiAvailability =
                GoogleApiAvailability.getInstance();
        final int connectionStatusCode =
                apiAvailability.isGooglePlayServicesAvailable(this);
        return connectionStatusCode == ConnectionResult.SUCCESS;
    }

    /**
     * Attempt to resolve a missing, out-of-date, invalid or disabled Google
     * Play Services installation via a user dialog, if possible.
     */
    private void acquireGooglePlayServices() {
        GoogleApiAvailability apiAvailability =
                GoogleApiAvailability.getInstance();
        final int connectionStatusCode =
                apiAvailability.isGooglePlayServicesAvailable(this);
        if (apiAvailability.isUserResolvableError(connectionStatusCode)) {
            showGooglePlayServicesAvailabilityErrorDialog(connectionStatusCode);
        }
    }


    /**
     * Display an error dialog showing that Google Play Services is missing
     * or out of date.
     * @param connectionStatusCode code describing the presence (or lack of)
     *     Google Play Services on this device.
     */
    void showGooglePlayServicesAvailabilityErrorDialog(
            final int connectionStatusCode) {
        GoogleApiAvailability apiAvailability = GoogleApiAvailability.getInstance();
        Dialog dialog = apiAvailability.getErrorDialog(
                MainActivity.this,
                connectionStatusCode,
                REQUEST_GOOGLE_PLAY_SERVICES);
        dialog.show();
    }

    /**
     * An asynchronous task that handles the YouTube Data API call.
     * Placing the API calls in their own task ensures the UI stays responsive.
     */
    private class MakeRequestTask extends AsyncTask<Void, Void, List<String>> {
        private com.google.api.services.youtube.YouTube mService = null;
        private Exception mLastError = null;

        MakeRequestTask(GoogleAccountCredential credential) {
            HttpTransport transport = AndroidHttp.newCompatibleTransport();
            JsonFactory jsonFactory = JacksonFactory.getDefaultInstance();
            mService = new com.google.api.services.youtube.YouTube.Builder(
                    transport, jsonFactory, credential)
                    .setApplicationName("YouTube Data API Android Quickstart")
                    .build();
        }

        /**
         * Background task to call YouTube Data API.
         * @param params no parameters needed for this task.
         */
        @Override
        protected List<String> doInBackground(Void... params) {
            try {
                return getDataFromApi();
            } catch (Exception e) {
                mLastError = e;
                cancel(true);
                return null;
            }
        }

        /**
         * Fetch information about the "GoogleDevelopers" YouTube channel.
         * @return List of Strings containing information about the channel.
         * @throws IOException
         */
        private List<String> getDataFromApi() throws IOException {
            // Get a list of up to 10 files.
            List<String> channelInfo = new ArrayList<String>();
            ChannelListResponse result = mService.channels().list("snippet,contentDetails,statistics")
                 .setForUsername("GoogleDevelopers")
                 .execute();
            List<Channel> channels = result.getItems();
            if (channels != null) {
                Channel channel = channels.get(0);
                channelInfo.add("This channel's ID is " + channel.getId() + ". " +
                        "Its title is '" + channel.getSnippet().getTitle() + ", " +
                        "and it has " + channel.getStatistics().getViewCount() + " views.");
            }
            return channelInfo;
        }

        @Override
        protected void onPreExecute() {
            mOutputText.setText("");
            mProgress.show();
        }

        @Override
        protected void onPostExecute(List<String> output) {
            mProgress.hide();
            if (output == null || output.size() == 0) {
                mOutputText.setText("No results returned.");
            } else {
                output.add(0, "Data retrieved using the YouTube Data API:");
                mOutputText.setText(TextUtils.join("\n", output));
            }
        }

        @Override
        protected void onCancelled() {
            mProgress.hide();
            if (mLastError != null) {
                if (mLastError instanceof GooglePlayServicesAvailabilityIOException) {
                    showGooglePlayServicesAvailabilityErrorDialog(
                            ((GooglePlayServicesAvailabilityIOException) mLastError)
                                    .getConnectionStatusCode());
                } else if (mLastError instanceof UserRecoverableAuthIOException) {
                    startActivityForResult(
                            ((UserRecoverableAuthIOException) mLastError).getIntent(),
                            MainActivity.REQUEST_AUTHORIZATION);
                } else {
                    mOutputText.setText("The following error occurred:\n"
                            + mLastError.getMessage());
                }
            } else {
                mOutputText.setText("Request cancelled.");
            }
        }
    }
}

步驟 6:執行應用程式

  1. 如要測試應用程式,請依序點選「Run」>「Run app」選單項目。
  2. 系統會提示您選取用來執行應用程式的已連線裝置 (建議) 或模擬。如果您要執行模擬,請確定設定為使用其中一個「使用 Google API 的」系統映像檔。如果您嘗試在尚未安裝 Google Play 服務的裝置上執行快速入門導覽課程,快速入門導覽課程會產生對話方塊讓您安裝。
  3. 如果是在模擬器上執行,請允許模擬器完全啟動並建立網路連線。
  4. 如果是首次啟動模擬器,您可能需要解鎖螢幕。無論如何,快速入門導覽課程應用程式應會自動啟動。
  5. 首次執行應用程式時,系統會提示您指定帳戶。完成登入流程,選擇要連結的帳戶。
  6. 選取帳戶後,應用程式會提示您授予存取權。按一下「OK」進行授權。

附註

  • 授權資訊會儲存在應用程式,因此後續的執行作業不會提示使用者進行授權。

延伸閱讀

疑難排解

未註冊的 Android 應用程式

如果 OAuth 對話方塊中包含「未註冊的 Android 應用程式」項目,表示找不到您在步驟 2 建立的 OAuth2 用戶端 ID,而 Android 將改回預設用戶端。預設用戶端不會設為使用此 API,因此如 accessNotConfigured. 等錯誤導致要求失敗,這些錯誤也可能提及預設專案編號 608941808256

如要修正這個問題,請確認您在步驟 1 中擷取的 SHA1 指紋與 build.gradle 檔案中列出的 applicationId,與您在 Google Developers Console 中設定的值完全一致。