Question

如何从Android设备中选择文件并发送到服务器。运行后，我的主要活动将导致onresume活动错误。因为在选择文件后，它会在运行时异常时给出nullpointer。

        btnUpload = (Button) findViewById(R.id.btnUploadPhoto);
        btnUpload.setOnClickListener(this);
        btnDownload.setOnClickListener(this);
    }

    private AndroidAuthSession buildSession() {
        AppKeyPair appKeyPair = new AppKeyPair(Constants.DROPBOX_APP_KEY,
                Constants.DROPBOX_APP_SECRET);
        AndroidAuthSession session;

        String[] stored = getKeys();
        if (stored != null) {
            AccessTokenPair accessToken = new AccessTokenPair(stored[0],
                    stored[1]);
            session = new AndroidAuthSession(appKeyPair, Constants.ACCESS_TYPE,
                    accessToken);
        } else {
            session = new AndroidAuthSession(appKeyPair, Constants.ACCESS_TYPE);
        }

        return session;
    }

    private String[] getKeys() {
        SharedPreferences prefs = getSharedPreferences(
                Constants.ACCOUNT_PREFS_NAME, 0);
        String key = prefs.getString(Constants.ACCESS_KEY_NAME, null);
        String secret = prefs.getString(Constants.ACCESS_SECRET_NAME, null);
        if (key != null && secret != null) {
            String[] ret = new String[2];
            ret[0] = key;
            ret[1] = secret;
            return ret;
        } else {
            return null;
        }
    }

    @Override
    public void onClick(View v) {
        if (v == btnDownload) {
            startActivity(new Intent(MainActivity.this, DropboxDownload.class));
        } else if (v == btnUpload) {
            createDir();
            if (mLoggedIn) {
                logOut();
            }
           // Intent intent = new Intent(Intent.ACTION_GET_CONTENT);

          // f = new File(Utils.getPath(),new Date().getTime()+".jpg");
          //  intent.putExtra(MediaStore.EXTRA_OUTPUT, Uri.fromFile(f));

            //  intent.setType("file/*");
          //  startActivityForResult(intent,TAKE_PHOTO);
            //Intent intent = new Intent(MediaStore.ACTION_GET_CONTENT);

         // startActivityForResult(intent, TAKE_PHOTO);


           /* Intent intent = new Intent();
            intent.setType("image/*");
            intent.setAction(Intent.ACTION_GET_CONTENT);
            startActivityForResult(intent, TAKE_PHOTO);    */

            Intent intent = new Intent(Intent.ACTION_GET_CONTENT);
            intent.addCategory(Intent.CATEGORY_OPENABLE);
            intent.setType("*/*");
            Intent f = Intent.createChooser(intent, "File");
            startActivityForResult(f, TAKE_PHOTO);



        }
    }

    private void logOut() {
        mApi.getSession().unlink();

        clearKeys();
    }

    private void clearKeys() {
        SharedPreferences prefs = getSharedPreferences(
                Constants.ACCOUNT_PREFS_NAME, 0);
        Editor edit = prefs.edit();
        edit.clear();
        edit.commit();
    }

    private void createDir() {
        File dir = new File(Utils.getPath());
        if (!dir.exists()) {
            dir.mkdirs();
        }
    }

    @Override
    protected void onActivityResult(int requestCode, int resultCode, Intent data) {
        super.onActivityResult(requestCode, resultCode, data);
        if (resultCode == RESULT_OK) {
            if (requestCode == TAKE_PHOTO) {
//              f = new File(Utils.getPath() + "/temp.jpg");
                if (Utils.isOnline(MainActivity.this)) {
                    mApi.getSession().startAuthentication(MainActivity.this);
                    onResume = true;
                } else {
                    Utils.showNetworkAlert(MainActivity.this);
                }
            }
        }
    }

    public void setLoggedIn(boolean loggedIn) {
        mLoggedIn = loggedIn;
        if (loggedIn) {
            UploadFile upload = new UploadFile(MainActivity.this, mApi, DIR, f);
            upload.execute();
            onResume = true;

        }
    }

    private void storeKeys(String key, String secret) {
        SharedPreferences prefs = getSharedPreferences(
                Constants.ACCOUNT_PREFS_NAME, 0);
        Editor edit = prefs.edit();
        edit.putString(Constants.ACCESS_KEY_NAME, key);
        edit.putString(Constants.ACCESS_SECRET_NAME, secret);
        edit.commit();
    }

    private void showToast(String msg) {
        Toast error = Toast.makeText(this, msg, Toast.LENGTH_LONG);
        error.show();
    }

    @Override
    protected void onResume() {

        AndroidAuthSession session = mApi.getSession();

        if (session.authenticationSuccessful()) {
            try {
                session.finishAuthentication();

                TokenPair tokens = session.getAccessTokenPair();
                storeKeys(tokens.key, tokens.secret);
                setLoggedIn(onResume);
            } catch (IllegalStateException e) {
                showToast("Couldn't authenticate with Dropbox:"
                        + e.getLocalizedMessage());
            }
        }
        super.onResume();
    }
}

这是我的崩溃报告：

01-25 13:30:20.629 9008-9008/com.example.pranit.cloudexample W/dalvikvm: threadid=1: thread exiting with uncaught exception (group=0x419eacf8)
01-25 13:30:20.629 9008-9008/com.example.pranit.cloudexample W/dalvikvm: threadid=1: uncaught exception occurred
01-25 13:30:20.630 9008-9008/com.example.pranit.cloudexample W/System.err: java.lang.RuntimeException: Unable to resume activity {com.example.pranit.cloudexample/com.example.pranit.cloudexample.MainActivity}: java.lang.NullPointerException
01-25 13:30:20.631 9008-9008/com.example.pranit.cloudexample W/System.err:     at android.app.ActivityThread.performResumeActivity(ActivityThread.java:3003)
01-25 13:30:20.631 9008-9008/com.example.pranit.cloudexample W/System.err:     at android.app.ActivityThread.handleResumeActivity(ActivityThread.java:3032)
01-25 13:30:20.631 9008-9008/com.example.pranit.cloudexample W/System.err:     at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1384)
01-25 13:30:20.632 9008-9008/com.example.pranit.cloudexample W/System.err:     at android.os.Handler.dispatchMessage(Handler.java:110)
01-25 13:30:20.632 9008-9008/com.example.pranit.cloudexample W/System.err:     at android.os.Looper.loop(Looper.java:193)
01-25 13:30:20.632 9008-9008/com.example.pranit.cloudexample W/System.err:     at android.app.ActivityThread.main(ActivityThread.java:5333)
01-25 13:30:20.632 9008-9008/com.example.pranit.cloudexample W/System.err:     at java.lang.reflect.Method.invokeNative(Native Method)
01-25 13:30:20.632 9008-9008/com.example.pranit.cloudexample W/System.err:     at java.lang.reflect.Method.invoke(Method.java:515)
01-25 13:30:20.632 9008-9008/com.example.pranit.cloudexample W/System.err:     at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:829)
01-25 13:30:20.632 9008-9008/com.example.pranit.cloudexample W/System.err:     at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:645)
01-25 13:30:20.633 9008-9008/com.example.pranit.cloudexample W/System.err:     at dalvik.system.NativeStart.main(Native Method)
01-25 13:30:20.633 9008-9008/com.example.pranit.cloudexample W/System.err: Caused by: java.lang.NullPointerException
01-25 13:30:20.638 9008-9008/com.example.pranit.cloudexample W/System.err:     at com.example.pranit.cloudexample.UploadFile.<init>(UploadFile.java:76)
01-25 13:30:20.638 9008-9008/com.example.pranit.cloudexample W/System.err:     at com.example.pranit.cloudexample.MainActivity.setLoggedIn(MainActivity.java:162)
01-25 13:30:20.638 9008-9008/com.example.pranit.cloudexample W/System.err:     at com.example.pranit.cloudexample.MainActivity.onResume(MainActivity.java:194)
01-25 13:30:20.639 9008-9008/com.example.pranit.cloudexample W/System.err:     at android.app.Instrumentation.callActivityOnResume(Instrumentation.java:1197)
01-25 13:30:20.639 9008-9008/com.example.pranit.cloudexample W/System.err:     at android.app.Activity.performResume(Activity.java:5422)
01-25 13:30:20.639 9008-9008/com.example.pranit.cloudexample W/System.err:     at android.app.ActivityThread.performResumeActivity(ActivityThread.java:2989)
01-25 13:30:20.640 9008-9008/com.example.pranit.cloudexample W/System.err:  ... 10 more
01-25 13:30:20.640 9008-9008/com.example.pranit.cloudexample W/dalvikvm: threadid=1: calling UncaughtExceptionHandler
01-25 13:30:20.647 9008-9008/com.example.pranit.cloudexample E/AndroidRuntime: FATAL EXCEPTION: main Process: com.example.pranit.cloudexample, PID: 9008
java.lang.RuntimeException: Unable to resume activity {com.example.pranit.cloudexample/com.example.pranit.cloudexample.MainActivity}: java.lang.NullPointerException
    at android.app.ActivityThread.performResumeActivity(ActivityThread.java:3003)
    at android.app.ActivityThread.handleResumeActivity(ActivityThread.java:3032)
    at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1384)
    at android.os.Handler.dispatchMessage(Handler.java:110)
    at android.os.Looper.loop(Looper.java:193)
    at android.app.ActivityThread.main(ActivityThread.java:5333)
    at java.lang.reflect.Method.invokeNative(Native Method)
    at java.lang.reflect.Method.invoke(Method.java:515)
    at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:829)
    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:645)
    at dalvik.system.NativeStart.main(Native Method)
Caused by: java.lang.NullPointerException
    at com.example.pranit.cloudexample.UploadFile.<init>(UploadFile.java:76)
    at com.example.pranit.cloudexample.MainActivity.setLoggedIn(MainActivity.java:162)
    at com.example.pranit.cloudexample.MainActivity.onResume(MainActivity.java:194)
    at android.app.Instrumentation.callActivityOnResume(Instrumentation.java:1197)
    at android.app.Activity.performResume(Activity.java:5422)
    at android.app.ActivityThread.performResumeActivity(ActivityThread.java:2989)
    at android.app.ActivityThread.handleResumeActivity(ActivityThread.java:3032) 
    at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1384) 
    at android.os.Handler.dispatchMessage(Handler.java:110)
    at android.os.Looper.loop(Looper.java:193) 
    at android.app.ActivityThread.main(ActivityThread.java:5333) 
    at java.lang.reflect.Method.invokeNative(Native Method) 
    at java.lang.reflect.Method.invoke(Method.java:515) 
    at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:829)
    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:645) 
    at dalvik.system.NativeStart.main(Native Method)

Answer 1

如果您的设备/模拟器＆gt; api 24

由于权限问题而产生此崩溃作为android M和N的新规则。因此，如果您正在为文件选择器工作，请为用户提供有关// GameScene.swift // StackOverflow // // Created by Sumner on 1/17/17. // Copyright © 2017 Sumner. All rights reserved. // import SpriteKit import GameplayKit class GameScene: SKScene { var cam: SKCameraNode! var sprite = SKSpriteNode(imageNamed: "sprite") var sprite2 = SKSpriteNode(imageNamed: "sprite2") let pauseLabel = SKLabelNode(text: "Pause!") /* * * START: NEW CODE * */ let gameNode = SKNode() var pauseMenuSprite: SKShapeNode! let pauseMenuTitleLabel = SKLabelNode(text: "Pause Menu") let pauseMenuContinueLabel = SKLabelNode(text: "Resume game?") let pauseMenuToMainMenuLabel = SKLabelNode(text: "Main Menu?") /* * * END: NEW CODE * */ var timeStart: Date! init(size: CGSize, difficulty: String) { super.init(size: size) gameDifficulty = difficulty timeStart = Date() /* * * START: NEW CODE * */ pauseMenuSprite = SKShapeNode(rectOf: size) /* * * END: NEW CODE * */ } required init?(coder aDecoder: NSCoder) { fatalError("init(coder:) has not been implemented") } override func didMove(to view: SKView) { backgroundColor = SKColor.white print("Game starting with \(gameDifficulty) difficulty") // Scale Sprites sprite.setScale(0.3) sprite2.setScale(0.3) sprite.position = CGPoint(x: size.width/4,y: size.height/2) sprite2.position = CGPoint(x: size.width/4 * 3,y: size.height/2) /* * * START: NEW CODE * */ gameNode.addChild(sprite) gameNode.addChild(sprite2) addChild(gameNode) /* * * END: NEW CODE * */ if gameDifficulty == "hard" { let sprite3 = SKSpriteNode(imageNamed: "sprite") sprite3.setScale(0.3) sprite3.position = CGPoint(x: size.width/4 * 2,y: size.height/2) addChild(sprite3) } pauseLabel.fontColor = SKColor.black pauseLabel.position = CGPoint(x: size.width/4 * 2,y: size.height/4) addChild(pauseLabel) } func touchDown(atPoint pos : CGPoint) { } func touchMoved(toPoint pos : CGPoint) { } func touchUp(atPoint pos : CGPoint) { } override func touchesBegan(_ touches: Set<UITouch>, with event: UIEvent?) { for t in touches { self.touchDown(atPoint: t.location(in: self)) } } override func touchesMoved(_ touches: Set<UITouch>, with event: UIEvent?) { for t in touches { self.touchMoved(toPoint: t.location(in: self)) } } override func touchesEnded(_ touches: Set<UITouch>, with event: UIEvent?) { let touch = touches.first let touchLocation = touch!.location(in: self) let pausedTouchLocation = touch?.location(in: pauseMenuSprite) if sprite.contains(touchLocation) { print("You tapped the blue sprite") /* let alert = UIAlertController(title: "Alert", message: "Message", preferredStyle: UIAlertControllerStyle.alert) let action = UIAlertAction(title: "Ok", style: .default) { action in // Handle when button is clicked let reveal = SKTransition.doorsOpenVertical(withDuration: 0.5) let menuScene = MenuScene(size: self.size) self.view?.presentScene(menuScene, transition: reveal) } alert.addAction(action) if let vc = self.scene?.view?.window?.rootViewController { vc.present(alert, animated: true, completion: nil) } */ } if sprite2.contains(touchLocation) { print("You tapped the purple sprite") let now = Date() let howLong = now.timeIntervalSinceReferenceDate - timeStart.timeIntervalSinceReferenceDate let reveal = SKTransition.doorsOpenVertical(withDuration: 0.5) let scoreScene = ScoreScene(size: self.size, score: howLong) self.view?.presentScene(scoreScene, transition: reveal) } /* * * START: NEW CODE * */ if pauseMenuContinueLabel.contains(pausedTouchLocation!) { pauseMenuSprite.removeFromParent() pauseMenuSprite.removeAllChildren() gameNode.isPaused = true } if pauseMenuToMainMenuLabel.contains(pausedTouchLocation!) { let reveal = SKTransition.doorsOpenVertical(withDuration: 0.5) let menuScene = MenuScene(size: self.size) self.view?.presentScene(menuScene, transition: reveal) } if pauseLabel.contains(touchLocation) { print("pause") setParametersForPauseMenu(size: size) addChild(pauseMenuSprite) gameNode.isPaused = true } /* * * END: NEW CODE * */ } override func touchesCancelled(_ touches: Set<UITouch>, with event: UIEvent?) { for t in touches { self.touchUp(atPoint: t.location(in: self)) } } override func update(_ currentTime: TimeInterval) { // Called before each frame is rendered } /* * * START: NEW CODE * */ func setParametersForPauseMenu(size: CGSize) { pauseMenuSprite.fillColor = SKColor.white pauseMenuSprite.alpha = 0.85 pauseMenuSprite.position = CGPoint(x: size.width / 2, y: size.height / 2) pauseMenuSprite.zPosition = 100 pauseMenuTitleLabel.fontColor = SKColor.black pauseMenuContinueLabel.fontColor = SKColor.black pauseMenuToMainMenuLabel.fontColor = SKColor.black pauseMenuTitleLabel.position = CGPoint(x: 0 ,y: size.height / 2 - pauseMenuSprite.frame.size.height / 6 ) pauseMenuContinueLabel.position = CGPoint(x: 0 ,y: size.height / 2 - pauseMenuSprite.frame.size.height / 6 * 4 ) pauseMenuToMainMenuLabel.position = CGPoint(x: 0 ,y: size.height / 2 - pauseMenuSprite.frame.size.height / 6 * 5) pauseMenuSprite.addChild(pauseMenuTitleLabel) pauseMenuSprite.addChild(pauseMenuContinueLabel) pauseMenuSprite.addChild(pauseMenuToMainMenuLabel) } /* * * END: NEW CODE * */ }和android.permission.WRITE_EXTERNAL_STORAGE

的问题的代码

或参考Android 6.0 Marshmallow. Cannot write to SD Card

其他分享崩溃日志。

Answer 2

@Pranit

尝试

@Override
protected void onResume() {
         super.onResume();

    AndroidAuthSession session = mApi.getSession();
   try {
    if (session.authenticationSuccessful()) {

            session.finishAuthentication();

            TokenPair tokens = session.getAccessTokenPair();
            storeKeys(tokens.key, tokens.secret);
            setLoggedIn(onResume);
          }
        } catch (IllegalStateException e) {
            showToast("Couldn't authenticate with Dropbox:"
                    + e.getLocalizedMessage());
        }


}

我想在android中实现文件选择器但是当我实现它时会给出空指针异常

2 个答案: