title: Install self signed Certificates via ADB
body: <p>I'm trying to install self-signed Certificates(created by Charles) via ADB
  I've pushed it to /sdcard/xxx.pem , And then failed to open it with Browsers that I could find, And Since the device removes the Setting Application, I could not install cert under the Setting App.
  Then I searched And try</p>
  
  <pre><code>am start -n com.android.certinstaller/.CertInstallerMain -a android.intent.action.VIEW -t application/x-x509-ca-cert file:///sdcard/test.cer
  </code></pre>
  
  <p>But just shown </p>
  
  <pre><code>01-07 17:47:56.442 12889-12889/com.android.certinstaller E/AndroidRuntime: FATAL EXCEPTION: main
  Process: com.android.certinstaller, PID: 12889
  java.lang.RuntimeException: Unable to start activity ComponentInfo{com.android.certinstaller/com.android.certinstaller.CertInstallerMain}: java.lang.NullPointerException: uri
      at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2416)
      at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2476)
      at android.app.ActivityThread.-wrap11(ActivityThread.java)
      at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1344)
      at android.os.Handler.dispatchMessage(Handler.java:102)
      at android.os.Looper.loop(Looper.java:148)
      at android.app.ActivityThread.main(ActivityThread.java:5418)
      at java.lang.reflect.Method.invoke(Native Method)
      at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:731)
      at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:621)
   Caused by: java.lang.NullPointerException: uri
      at com.android.internal.util.Preconditions.checkNotNull(Preconditions.java:60)
      at android.content.ContentResolver.openInputStream(ContentResolver.java:645)
      at com.android.certinstaller.CertInstallerMain.startInstallActivity(CertInstallerMain.java:139)
      at com.android.certinstaller.CertInstallerMain.onCreate(CertInstallerMain.java:119)
      at android.app.Activity.performCreate(Activity.java:6270)
      at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1115)
      at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2369)
      at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2476) 
      at android.app.ActivityThread.-wrap11(ActivityThread.java) 
      at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1344) 
      at android.os.Handler.dispatchMessage(Handler.java:102) 
      at android.os.Looper.loop(Looper.java:148) 
      at android.app.ActivityThread.main(ActivityThread.java:5418) 
      at java.lang.reflect.Method.invoke(Native Method) 
  </code></pre>
  
  <p>I'm not familiar with this com.android.certinstaller app, Is there any reference How I could use it to install a cert?</p>