Error: Unable to capture screenshot - Android hybr

I'm using Protractor for test automation. I tested my hybrid Android app perfectly using Protractor (jasmine) and Appium. But I can not get the browser.takeScreenshot() function to work properly. All other test work perfectly like clicking buttons or stuff like that. I created a new blank app to rule out that a plugin causes this problem. No Cordova Plugin prevents the screenshot capability and I am able to take screenshots with the android device itself.
I tried this StackOverflow answer (and many many more), but with no success (and it seems like nobody ever experienced this issue).
I also used the protractor-jasmin2-screenshot-reporter to rule out, that my code for taking the screenshot is not working, but I get the same result. Intresstingly, when I use browserName: 'Chrome' and let the test open Chrome on my device and call www.google.com and let my code take a screenshot, it works fine. Only in my hybrid app, taking a screenshot does not work.
(The browser.takeScreenshot().then(function (png) {... code is from the official protractor page and other reliable sources).

My Specs

Protractor: 5.0.0
Appium (Desktop Client): 1.4.16.1 (latest version)
Windows 10 Enterprise 64 Bit
Chromedriver: 2.27 (latest version)
Angular: 1.5.3
Node.js: 6.9.1
Android: 6.0.1 and 4.4.2 (Galaxy S6 and Alcatel Pixi)
Cordova 6.4.0

My Protractor config.js

exports.config = {

    seleniumAddress : 'http://localhost:4723/wd/hub',

    // Reference: https://github.com/appium/sample-code/blob/master/sample-code/examples/node/helpers/caps.js
    capabilities : {
        // needed by local appium
        platformVersion : '',
        platformName : '',
        deviceName : '',
        // needed by protractor
        browserName : '',
        autoWebview : true,
        // CHANGE THIS TO YOUR ABSOLUTE PATH OR SET IT IN APPIUM CLIENT
        app : 'C:/Projekte/WifiWizardTestApp/platforms/android/build/outputs/apk/android-debug.apk',
        newCommandTimeout : 60
    },

    //needed for local appium
    baseUrl : 'http://localhost:8080',

    //configuring wd in onPrepare
    //wdBridge helps to bridge wd driver with other selenium clients
    //See https://github.com/sebv/wd-bridge/blob/master/README.md
    onPrepare : function () {
        var wd = require('wd');
        var protractor = require('protractor');
        var wdBridge = require('wd-bridge')(protractor, wd);
        wdBridge.initFromProtractor(exports.config);
    },
};

My test.spec.js

var fs = require('fs');

describe('Testing the browse state', function () {

    it('should be able to take a screenshot', function (done) {
        browser.sleep(2000);

        browser.takeScreenshot().then(function (png) {
            console.log('browser.takeScreenshot()');
            var stream = fs.createWriteStream('screenshot.png');
            stream.write(new Buffer(png, 'base64'));
            stream.end();
            done();
        });
    });

    it('should be able to take an other screenshot', function () {

        browser.takeScreenshot().then(function (png) {
            console.log('browser.takeScreenshot()');
            var stream = fs.createWriteStream('screenshot2.png');
            stream.write(new Buffer(png, 'base64'));
            stream.end();
        });
    });
});

My console output (Android 6.0.1)

C:\Projekte\WifiWizardTestApp>protractor protractor.config.js --specs tests/browse.spec.js
[09:27:44] I/hosted - Using the selenium server at http://localhost:4723/wd/hub
[09:27:44] I/launcher - Running 1 instances of WebDriver
Started
A Jasmine spec timed out. Resetting the WebDriver Control Flow.
FA Jasmine spec timed out. Resetting the WebDriver Control Flow.
F

Failures:
1) Testing the browse state should be able to take a screenshot
  Message:
    Error: Timeout - Async callback was not invoked within timeout specified by jasmine.DEFAULT_TIMEOUT_INTERVAL.
  Stack:
    Error: Timeout - Async callback was not invoked within timeout specified by jasmine.DEFAULT_TIMEOUT_INTERVAL.
        at ontimeout (timers.js:365:14)
        at tryOnTimeout (timers.js:237:5)
        at Timer.listOnTimeout (timers.js:207:5)

2) Testing the browse state should be able to take an other screenshot
  Message:
    Error: Timeout - Async callback was not invoked within timeout specified by jasmine.DEFAULT_TIMEOUT_INTERVAL.
  Stack:
    Error: Timeout - Async callback was not invoked within timeout specified by jasmine.DEFAULT_TIMEOUT_INTERVAL.
        at ontimeout (timers.js:365:14)
        at tryOnTimeout (timers.js:237:5)
        at Timer.listOnTimeout (timers.js:207:5)

2 specs, 2 failures
Finished in 60.04 seconds

My console output (Android 4.4.2)

C:\Projekte\WifiWizardTestApp>protractor protractor.config.js --specs tests/browse.spec.js
[15:15:49] I/hosted - Using the selenium server at http://localhost:4723/wd/hub
[15:15:49] I/launcher - Running 1 instances of WebDriver
Started
FF

Failures:
1) Testing the browse state should be able to take a screenshot
  Message:
    Failed: unknown error: unhandled inspector error: {"code":-32603,"message":"Unable to capture screenshot"}
      (Session info: webview=30.0.0.0)
      (Driver info: chromedriver=2.27.440174 (e97a722caafc2d3a8b807ee115bfb307f7d2cfd9),platform=Windows NT 10.0.10586 x86_64)
  Stack:
    WebDriverError: unknown error: unhandled inspector error: {"code":-32603,"message":"Unable to capture screenshot"}
      (Session info: webview=30.0.0.0)
      (Driver info: chromedriver=2.27.440174 (e97a722caafc2d3a8b807ee115bfb307f7d2cfd9),platform=Windows NT 10.0.10586 x86_64)
        at WebDriverError (C:\Users\mkaiser\AppData\Roaming\npm\node_modules\protractor\node_modules\selenium-webdriver\lib\error.js:27:5)
        at Object.checkLegacyResponse (C:\Users\mkaiser\AppData\Roaming\npm\node_modules\protractor\node_modules\selenium-webdriver\lib\error.js:505:15)
        at parseHttpResponse (C:\Users\mkaiser\AppData\Roaming\npm\node_modules\protractor\node_modules\selenium-webdriver\lib\http.js:509:13)
        at doSend.then.response (C:\Users\mkaiser\AppData\Roaming\npm\node_modules\protractor\node_modules\selenium-webdriver\lib\http.js:440:13)
        at process._tickCallback (internal/process/next_tick.js:103:7)
    From: Task: WebDriver.takeScreenshot()
        at WebDriver.schedule (C:\Users\mkaiser\AppData\Roaming\npm\node_modules\protractor\node_modules\selenium-webdriver\lib\webdriver.js:816:17)
        at WebDriver.takeScreenshot (C:\Users\mkaiser\AppData\Roaming\npm\node_modules\protractor\node_modules\selenium-webdriver\lib\webdriver.js:1092:17)
        at ProtractorBrowser.to.(anonymous function) [as takeScreenshot] (C:\Users\mkaiser\AppData\Roaming\npm\node_modules\protractor\lib\browser.ts:94:25)
        at Object.<anonymous> (C:\Projekte\WifiWizardTestApp\tests\browse.spec.js:14:17)
        at C:\Users\mkaiser\AppData\Roaming\npm\node_modules\protractor\node_modules\jasminewd2\index.js:98:15
        at new ManagedPromise (C:\Users\mkaiser\AppData\Roaming\npm\node_modules\protractor\node_modules\selenium-webdriver\lib\promise.js:1067:7)
        at controlFlowExecute (C:\Users\mkaiser\AppData\Roaming\npm\node_modules\protractor\node_modules\jasminewd2\index.js:87:18)
        at TaskQueue.execute_ (C:\Users\mkaiser\AppData\Roaming\npm\node_modules\protractor\node_modules\selenium-webdriver\lib\promise.js:2970:14)
        at TaskQueue.executeNext_ (C:\Users\mkaiser\AppData\Roaming\npm\node_modules\protractor\node_modules\selenium-webdriver\lib\promise.js:2953:27)
        at asyncRun (C:\Users\mkaiser\AppData\Roaming\npm\node_modules\protractor\node_modules\selenium-webdriver\lib\promise.js:2813:27)
    From: Task: Run it("should be able to take a screenshot") in control flow
        at Object.<anonymous> (C:\Users\mkaiser\AppData\Roaming\npm\node_modules\protractor\node_modules\jasminewd2\index.js:86:14)
    From asynchronous test:
    Error
        at Suite.<anonymous> (C:\Projekte\WifiWizardTestApp\tests\browse.spec.js:8:5)
        at Object.<anonymous> (C:\Projekte\WifiWizardTestApp\tests\browse.spec.js:4:1)
        at Module._compile (module.js:570:32)
        at Object.Module._extensions..js (module.js:579:10)
        at Module.load (module.js:487:32)
        at tryModuleLoad (module.js:446:12)

2) Testing the browse state should be able to take an other screenshot
  Message:
    Failed: unknown error: unhandled inspector error: {"code":-32603,"message":"Unable to capture screenshot"}
      (Session info: webview=30.0.0.0)
      (Driver info: chromedriver=2.27.440174 (e97a722caafc2d3a8b807ee115bfb307f7d2cfd9),platform=Windows NT 10.0.10586 x86_64)
  Stack:
    WebDriverError: unknown error: unhandled inspector error: {"code":-32603,"message":"Unable to capture screenshot"}
      (Session info: webview=30.0.0.0)
      (Driver info: chromedriver=2.27.440174 (e97a722caafc2d3a8b807ee115bfb307f7d2cfd9),platform=Windows NT 10.0.10586 x86_64)
        at WebDriverError (C:\Users\mkaiser\AppData\Roaming\npm\node_modules\protractor\node_modules\selenium-webdriver\lib\error.js:27:5)
        at Object.checkLegacyResponse (C:\Users\mkaiser\AppData\Roaming\npm\node_modules\protractor\node_modules\selenium-webdriver\lib\error.js:505:15)
        at parseHttpResponse (C:\Users\mkaiser\AppData\Roaming\npm\node_modules\protractor\node_modules\selenium-webdriver\lib\http.js:509:13)
        at doSend.then.response (C:\Users\mkaiser\AppData\Roaming\npm\node_modules\protractor\node_modules\selenium-webdriver\lib\http.js:440:13)
        at process._tickCallback (internal/process/next_tick.js:103:7)
    From: Task: WebDriver.takeScreenshot()
        at WebDriver.schedule (C:\Users\mkaiser\AppData\Roaming\npm\node_modules\protractor\node_modules\selenium-webdriver\lib\webdriver.js:816:17)
        at WebDriver.takeScreenshot (C:\Users\mkaiser\AppData\Roaming\npm\node_modules\protractor\node_modules\selenium-webdriver\lib\webdriver.js:1092:17)
        at ProtractorBrowser.to.(anonymous function) [as takeScreenshot] (C:\Users\mkaiser\AppData\Roaming\npm\node_modules\protractor\lib\browser.ts:94:25)
        at Object.<anonymous> (C:\Projekte\WifiWizardTestApp\tests\browse.spec.js:26:17)
        at C:\Users\mkaiser\AppData\Roaming\npm\node_modules\protractor\node_modules\jasminewd2\index.js:102:25
        at new ManagedPromise (C:\Users\mkaiser\AppData\Roaming\npm\node_modules\protractor\node_modules\selenium-webdriver\lib\promise.js:1067:7)
        at controlFlowExecute (C:\Users\mkaiser\AppData\Roaming\npm\node_modules\protractor\node_modules\jasminewd2\index.js:87:18)
        at TaskQueue.execute_ (C:\Users\mkaiser\AppData\Roaming\npm\node_modules\protractor\node_modules\selenium-webdriver\lib\promise.js:2970:14)
        at TaskQueue.executeNext_ (C:\Users\mkaiser\AppData\Roaming\npm\node_modules\protractor\node_modules\selenium-webdriver\lib\promise.js:2953:27)
        at asyncRun (C:\Users\mkaiser\AppData\Roaming\npm\node_modules\protractor\node_modules\selenium-webdriver\lib\promise.js:2860:25)
    From: Task: Run it("should be able to take an other screenshot") in control flow
        at Object.<anonymous> (C:\Users\mkaiser\AppData\Roaming\npm\node_modules\protractor\node_modules\jasminewd2\index.js:86:14)
    From asynchronous test:
    Error
        at Suite.<anonymous> (C:\Projekte\WifiWizardTestApp\tests\browse.spec.js:24:5)
        at Object.<anonymous> (C:\Projekte\WifiWizardTestApp\tests\browse.spec.js:4:1)
        at Module._compile (module.js:570:32)
        at Object.Module._extensions..js (module.js:579:10)
        at Module.load (module.js:487:32)
        at tryModuleLoad (module.js:446:12)

2 specs, 2 failures
Finished in 2.258 seconds
[15:17:49] I/launcher - 0 instance(s) of WebDriver still running
[15:17:49] I/launcher -  #01 failed 2 test(s)
[15:17:49] I/launcher - overall: 2 failed spec(s)
[15:17:49] E/launcher - Process exited with error code 1

回答1:

    wdBrowser.context('NATIVE_APP').then(() => {
        browser.takeScreenshot().then(function (png) {
             console.log('browser.takeScreenshot()');
             var stream = fs.createWriteStream('screenshot.png');
             stream.write(new Buffer(png, 'base64'));
             stream.end(function(){
                  wdBrowser.context(<Your webview>).then(done);
             });
        })
    });

Where wdBrowser is a global variable set by wdBridge. Should work - been having a similar issue (unable to take screenshot but no error message like you have)

You can grab your webview name/id from the appium logs.

回答2:

the wdBrowser.context('NATIVE_APP') didn't work for me.
It took the pictures, but afterwards each testcase failed.

I found a different solution to take screenshots.
I replaced the takeScreenshots() method with following code:

  var exec = require('child_process').exec;
  exec('adb shell /system/bin/screencap -p /sdcard/' + filename); // Take a screenshot and store it on the internal storage.

  // Wait until the screenshot is created on android
  var date = new Date();
  var curDate = null;
  do {
      curDate = new Date();
  }
  while (curDate - date < 1000);

  var command = 'adb pull /sdcard/'+ filename + ' ' + screenshotPath;
  exec(command, function (err, stdout, stderr) {  // Copy the screenshot from the internal storage to the local computer. 
      if(err){
        console.error('The screenshot could not be copied from the ANDROID device: ' + stdout);
        console.log('The screenshot is stored on the ANDROID device with the name: ' + filename);
      }
  });

I had following problems:

The screenshot was not created until I wanted to pull it.
The screenshot file existed during the pull, but it only pulled 0kb files. Therefore I implemented a one second sleep between taking the screenshot and pulling it to the computer.