You might see any one or more of the following options:.
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Content and code samples on this page are subject to the licenses described in the Content License. Last updated June 5, Android Studio provides a debugger that allows you to do the following and more: Select a device to debug your app on. Examine variables and evaluate expressions at runtime. Enable debugging Before you can begin debugging, you need to prepare as follows: Enable debugging on your device: Start debugging You can start a debugging session as follows: Set some breakpoints in the app code.
In the toolbar, click Debug to display the Select Deployment Target window. Select a deployment target and click OK. The Debugger window, showing the current thread and the object tree for a variable Attach the debugger to a running app If your app is already running on your device, you can start debugging without restarting your app as follows: Click Attach debugger to Android process.
In the Choose Process dialog, select the process you want to attach the debugger to. The Debug window appears. The debug types available include the following: Select if you want Android Studio to automatically choose the best option for the code you are debugging. Otherwise, Android Studio uses the Java debug type. Select if you want to debug only code written in Java or Kotlin—the Java debugger ignores any breakpoints or watches you set in your native code.
Native debugging works with only Android 4. Select if you want to switch between debugging both Java and native code. Android Studio attaches both the Java debugger and LLDB to your app process, one for the Java debugger and one for LLDB, so you can inspect breakpoints in both your Java and native code without restarting your app or changing your debug configuration. Tab for debugging native code and tab for debugging Java code Note: Use the system log The system log shows system messages while you debug your app.
Write log messages in your code To write log messages in your code, use the Log class. The following example shows how you might add log messages to determine if previous state information is available when your activity starts: View the system log You can view and filter debug and other system messages in the Logcat window. Logcat window with filter settings For a description of logcat and its filtering options, see Write and view logs with Logcat. Work with breakpoints Android Studio supports several types of breakpoints that trigger different debugging actions.
View properties by scope
To add a line breakpoint, proceed as follows: If your app is already running, you don't need to update it to add the breakpoint—just click Attach debugger to Android proccess. Otherwise, start debugging by clicking Debug. A red dot appears next to the line when you set a breakpoint When your code execution reaches the breakpoint, Android Studio pauses execution of your app. You can then use the tools in the Debugger tab to identify the state of the app: The Frames , Variables , and Watches panes are also available and work exactly as they would if you were debugging Java code.
Although the Threads pane is not available in the LLDB session view, you can access your app processes using the drop-down list in the Frames pane.
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You can learn more about these panes in the sections about how to debug window frames and inspect variables. If you have certain commands that you would like LLDB to execute each time you start debugging your app, either just before or just after the debugger attaches to your app process, you can add those commands to your debug configuration. View and configure breakpoints To view all the breakpoints and configure breakpoint settings, click View Breakpoints on the left side of the Debug window.
The Breakpoints window lists all the current breakpoints and includes behavior settings for each The Breakpoints window lets you enable or disable each breakpoint from the list on the left. Debug window frames In the Debugger window, the Frames pane lets you inspect the stack frame that caused the current breakpoint to be hit.
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Inspect variables In the Debugger window, the Variables pane lets you inspect variables when the system stops your app on a breakpoint and you select a frame from the Frames pane. To add a variable or expression to the Watches list, follow these steps: In the Watches pane, click Add. In the text box that appears, type the name of the variable or expression you want to watch and then press Enter. To set a watchpoint, you must meet the following requirements: Other devices may support fewer watchpoints.
If you meet the requirements above, you can add a watchpoint as follows: While your app is suspended on a breakpoint, navigate to the Variables pane in your LLDB session view. Adding a watchpoint to a variable in memory Configure your watchpoint with the following options: You can deselect this option if you want to tell Android Studio to ignore the watchpoint for the time being.
Android Studio still saves your watchpoint so you can access it later in your debug session. By default, the Android system suspends your app process when it accesses a block of memory you assign to a watchpoint. Log message to console and Remove [the watchpoint] when hit. Select whether your app should trigger your watchpoint when it tries to Read or Write to the block of memory the system allocates to the variable.
To trigger your watchpoint on either a read or write, select Any. The Breakpoints dialogue lists your current watchpoints and includes behavior settings for each After you add your watchpoint, click Resume Program on the left side of the Debug window to resume your app process. Android Studio indicates the line of code that your app executes just before triggering a watchpoint View and change resource value display format In debug mode, you can view resource values and select a different display format for variables in your Java code.
From there you can inspect the variables at that execution context in the Locals and Watch panes.
The Console pane of the debugger provides a console for executing script statements on-the-fly. Type any valid statement or variable name, and press ENTER or click Run Script to execute that statement in the context of the current page and right where execution is paused. Clicking the Multi Line Mode button expands the input window to allow entry of multiple lines.
How to step through your code
It also changes the behavior of the ENTER key, such that the key creates a new line instead of executing the script. Here, you can type multiple lines of code and then execute them by clicking Run Script. The input window, which is resizable, offers additional controls through the shortcut menu. You can use the Console pane at any time, even if debugger is not started. When execution stops at a breakpoint, the commands entered in this pane will run in the execution scope of the breakpoint; when execution is not paused, the commands will run in the global scope.
All the script errors in a particular instance of Windows Internet Explorer are logged to the Console pane once the Developer Tools is open. To navigate to the error location, click the source information provided in the error. You can also log messages to the Console by using console.
Instead of using window. To differentiate between messages, use different console. These console commands can be called with a list of arguments that will be concatenated to generate the output string. The arguments can also be formatted by using substitution patterns in the style of printf. For example, you can call console. These console messages can be filtered from the console pane to show or hide.
To select the messages you want to show or hide from the Console pane, set the Filter as follows: A list of available filters appears where the filter with a check mark is active. In addition, the console object can be extended to add new functionalities to your development needs. For example, you might want a customized method to output your debugging messages to the console. To add a console. The preceding example takes in two arguments and simply outputs them to the Console pane with minimal formating.
All the items below it are functions which were executed before entering this function — in this case, we can see the function where the code came from is an anonymous function. We can access all the previous functions by clicking them in the call stack list. We should try and repeat our previous steps until we find the source: Look for any variables which are being passed around with incorrect values. Entering the previous function, we again get the same information the script had — all the variable values etc.
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We can also see the line of code which called our original function. If this was real code, you could now fix this problem — but in this case I typed this into the console to trigger an error. This code is based on some real production code we have at my day job, but simplified so we can focus on debugging, rather than understanding what the code is doing.
This code has some logic to generate a list of objects based on any element with a class in the document. The bug here is that we want the type to indicate "image" when the element is an IMG , but it says "other" instead. To pause code execution anywhere we like, we can use a breakpoint. We have two ways to set a breakpoint:. If we click on the run button after adding the debugger statement remember to re-run the fiddle to save the changes , the script debugger will automatically pause code on the line where the statement is.
We can see that the iteration of the forEach is currently in the div element. We want to see what happens for the image element. To do so, we can resume script execution using the button on the right that looks like a Play button.
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